You could stand to be more explicit about precisely whom Mike and Linda are metaphors for, since it affects how to interpret your analogy: it's clear the "other woman" here is Trump/fascism, but Linda could be any of (the Democratic Party, the establishment of both parties/the Uniparty, the Democratic voters) and Mike could be (the Republican Party, the electorate at large, the Republican voters).
If Mike is the electorate at large, then the correct response is that they're not married, and he just wants casual one-night stands (or two–four year stands), and Linda (whether she be the Democratic Party or the Uniparty) ought to follow Jenny's advice.
If Linda and Mike are the voters of the two opposing parties, then again, Linda is deluded about them being married instead of merely acrimonious roommates who have no say in whom the other sleeps with, and she clearly ought to follow Francine's advice.
Now, if they're standing in for the establishments of the two parties, then, okay, you could reasonably consider there to be a "marriage" here to preserve, and they could go to couples counseling or whatever to realize they've both become too vulnerable to the whims of their primary bases, and agree to coördinate a return to the lauded "smoke-filled rooms" of the past to choose their candidates, as they did before the reforms of circa 1970.
Update: Edited the beginning of the second section to make the analogy more clear, in response to a suggestion in the comments.
Linda discovers evidence that her faithful spouse of many years, Mike, has engaged in sexual infidelity. When she initially confronts him, Mike contritely assures Linda that there was only one, fleeting indiscretion which will never repeat itself. But Linda later discovers that Mike is actually having a full-blown affair.
When she turns to her friends for support, Linda receives two conflicting pieces of unsolicited advice. Jenny suggests that Linda should start hitting the gym and spice things up in the bedroom with Mike, to win him back from her rival. Francine introduces Linda to dating apps, suggesting that Linda may have to accept an open marriage with Mike.
Whose advice is better? Obviously a trick question: both are so terrible to be unbelievable as advice given by normal people in the real world. Jenny's is patently demeaning, reducing Linda to nothing but a gig worker who must compete with other women for Mike's custom in sexual gratification. Francine's advice at least recognizes some parity between Jenny and Mike, but not as partners with one another, only as equal contributors and participants in an open market for sex. Certainly, there are open marriages that maintain trust without sexual monogamy. But a modern closed marriage -- that is, an equal partnership in which sexual monogamy is expected of both partners -- doesn't just revert benignly to an open one through one partner engaging in extramarital sex. Such an act is a betrayal against the whole partnership. In meaningful faith-based partnerships, betrayal brings painful consequences; whatever pleasure Mike derives from it must be intermixed with guilt, shame, and fear of discovery, retaliation, and an acrimonious collapse of the marriage. That makes the affair about as far from "just sex" as can possibly be. For Linda to respond to it otherwise would be the most grievous betrayal of all: demonstrating such indifference to the marriage that she can't be bothered to defend it.
Explaining this feels silly, because it is intuitively obvious. So why contrive characters giving absurd advice? Because Jenny and Francine's advice is analogous to what is currently on offer in the popular discourse on America's path through Trumpism.
A polity is a partnership, demanding loyalty to some set of shared principles that trump the pursuit of personal gain or subgroup advantage. If an elected official is caught selling American secrets to the highest bidder, one ought not ask what party he belongs to before deciding whether to feel outrage, or substitute it with admiration for his business acumen when learning of the price.
The Trumpist movement regularly deploys expressions of outrage and promises of retribution, often against an 'establishment' that has sold out 'real Americans.' This message of retaliation against trust betrayed depends on some notion of trust having once existed.
The anti-Trump opposition, for its part, has been vocal in its alarm at Trumpism's attacks on the rule of law and other fundamental republican principles. But in practice this alarm has yet to translate into any response appropriate to a critical breach in the republican contract. Past the holding action of lawsuits against the Trump administration, the only solution the anti-Trumpists seems to have in mind is for Democrats to woo enough voters on policy to win back Congress in the midterms and the White House in 2028. As the Democrats' appeal to "save democracy" was insufficient to prevent the election of an authoritarian in 2024, it apparently must follow that democracy, through the instrument of the party not taken over by Trumpism, should "sexy itself up" in other ways, per Jenny's advice, to make fidelity to it more attractive.
More recently, the demeaning asymmetry of a one-sided adherence to republican principle appears to have been recognized, but the correction has Democrats embrace Trumpist tactics merely to level the competitive playing field and protect their own policy preferences. This is equivalent to Francine's advice to start dating, injecting into Jenny's completely amoral ideas a notion of parity and self-respect. But it is tantamount to acknowledging that the "save our democracy" alarmism was just a rhetorical expression of inessential partisan preferences; "democracy" refers not to a shared, morally binding project, just the conditions most amenable to Democrats' goals. Under that interpretation, however inviolable the old rules appeared, it was only because they had never been violated; now that they have, Democrats must 'democratically' allow stuffy conventions to fall by the wayside.
Consider specifically a piece recently published in The Atlantic contemplating a future in which the Democratic Party acquiesces to Trump's unilateral redefinition of executive power but leveraging it to "undo the damage" done by his administration after retaking the White House. The author, former DHS deputy assistant secretary Paul Rosenzweig, points out that this is not a future favorable to Democrats' policy interests: in a series of alternating pendulum swings between liberal Democratic presidents and "Trump-aligned" Republicans, each using executive power to tear down the previous administration's policies, the net result would favor the conservative project of crippling the federal government. Yet, in declaring that this is what lies ahead, Rosenzweig implies that it's the best anyone can do.
Note that Rosenzweig does nothing to justify his chosen model for the future of American politics, that canonical representation of orderly and harmonious transfer of power, the pendulum. This is surprising, given Trump's distinguished refusal of an orderly transfer of power in 2021. Somehow though, Democrats are still assured that the pendulum will swing ever on. To make this work, Rosenzweig interprets Trumpism as an instrument for giving Republicans what they have always wanted, a hamstrung federal government, and having attained the object of their true desire, they have no reason to go further. At the same time, Democrats having lost an object of their desire, a functioning federal government, will nevertheless restrain themselves to do no more than exactly what has already been done to them by Republicans, presumably out of a democratic respect for self-restraint. Thus Rosenzweig must conclude that the Republicans and Democrats have each priced in the other's responses as the cost of doing business, and a new stable equilibrium has been attained, like Francine's belief that Linda and Mike's marriage will simply continue as before, altered only with sex with other people.
Of course, what small-d democrats truly fear is not a stable "rightward" skew in government policy but the collapse of the shared democratic project. It is not the metaphorical "extramarital sex" itself but the rule-breaking and where it ultimately is leading. The obvious failure mode currently in play is for Trump (or, if not him, some even less restrained future executive) to use the unprecedented power granted to him by the Supreme Court to prevent the opposition from ever returning to power. The fact that this risk is now so easily imaginable -- was stated clearly in Justice Sotomayor's dissent to one of the shocking opinions granting that power, when she presented the hypothetical of a president ordering Seal Team 6 to assassinate political rivals -- creates an unstable race to be the party to do it first. A non-escalatory posture, proposing no novel applications of unrestrained executive power beyond those exercised by Trump, does make sense to dampen the race condition. But it does nothing to signal that democratic norms are mutually binding and worth defending at all costs. If the pendulum keeps swinging, it will feature government by two parties that are both undermining democracy: one actively, the other by passive, cautious imitation.
So if Mike's affair is not "just sex," what is it about? Let's suppose that Linda and Mike have had many good years together, but for a while now their marriage has struggled. Money troubles play a big role: they wanted the kids to go to the best public schools, so they bought into a neighborhood they can barely afford. Now they both work all the time to afford the mortgage, at jobs they dislike. For a long period whatever alone time they had was poisoned by venting about the jobs they despised, so presently they avoid interacting alone and double down on work and parenting.
Linda and Mike's marriage suffers from an over-commitment problem. Ownership of the house exacts a high toll on the happiness of their marriage, but represents their commitment to being good parents to their children (a promise they implicitly made when having children, one no less binding than their marriage vows). Desperate for happiness, Mike forces the issue by betraying the marriage explicitly. Although, in the moment, Mike may rationalize the affair as retribution for Linda's lack of attentiveness, upon examination this is not the ultimate cause. Linda may, indeed, have been particularly unreasonable about her definition of good parenting. Or perhaps Mike's pride has been the primary obstacle. Or perhaps they are both equally invested in the house. In all three cases, the crisis of the affair creates an opportunity to move forward. Linda can grant Mike absolution for his blatant but short-lived betrayal as payback for her own quiet, slow form of betrayal in the first case. In the second, with his infidelity all pride is lost to shame, as he hands Linda leverage to make him concede the house in the bargain over reconciliation and forgiveness. In the third the affair provides a wake-up call to find the roots of their unhappiness. Reinstating a healthy partnership will demand flexibility in the construction of a shared narrative of transgression, repentance, and renewal.
Even if misunderstanding and hostility prevent Mike and Linda from an amicable reconciliation, dynamics of transgression, pain, and renewal will play out naturally; the structure is the same but the costs may be higher. In addition to losing the house, ongoing legal battles, and so on, they will properly feel the sting of failure and should expect to be held to account by prospective new partners for it. We enter into commitments to achieve goals we can't achieve on our own, and backing out of them requires paying a price before moving on and trying again elsewhere.
Politics also requires commitment; power is granted for promises about what to do, or not to do, with that power. Sometimes the commitments become too burdensome and unreasonably demanding, dragging the partnership down into a dysfunctional rut. Enduring partisanship on a problematic issue is as much a failure mode as consensus around a bad status quo, being just a consensus to keep fighting and move nowhere. Rosenzweig is on to something when pointing out the net effect of Trumpism on the average position, so to speak, of the swinging pendulum. Because, with or without Trump, it's the commitment to the well-defined boundaries of the pendulum swing that can form the rut, creating conditions of discontent that might lead to cooperative collapse. As with a failed marriage, cooperative collapse will solve the commitment problem, as all commitments become null and void; it's just a question of what price must be paid before starting again.
Imagine the following alternate timeline: its version of President Trump, not only unchecked but unhinged and undeterred by the Sword of Damocles, orders a nuclear strike against Camden, New Jersey, a strongly Democratic and overwhelmingly Hispanic and Black city. The strike cows the states into installing Trump-aligned governors and ratifying a set of constitutional amendments which repeal presidential term limits and explicitly grant the president the power to qualify all candidates for federal office. Trump subsequently disqualifies non-Trumpists from running for office, so that after the midterms the country is effectively under 'permanent' one-party rule. Nature, however, intervenes, by striking the elderly Trump down with dementia (sic semper tyrannis). When his crony cabinet hesitates at deploying the 25th Amendment to depose the incapacitated strongman, an underground anti-Trump coalition seizes the moment to lead a revolt against one-party rule, backed by a faction in the military that was sickened by the chain of command allowing the nuking of American civilians, which cements the rebels' victory.
The nascent restored republic, however, lacks a workable constitution: the version that exists is a perverted instrument of authoritarian rule, while the version that preceded it contained the genesis of that perversion. For very similar reasons the republic needs new political parties and elites: the existing Republican Party is obviously hopelessly riddled with Trumpist collaborators, but the old Democratic Party also is culpable for failing to prevent the rise of Trumpism. High rank in the old order is like a millstone sending its wearers to the bottom, demanding atonement and actual usefulness to the new order if they are to be released from it. Happily, the rebellion itself has forged new leaders with proven patriotism and no stake in the petty squabbles of the past, whose hands are untied to govern through the restoration and ratification of a reformed constitution. As the crisis fades the spirit of unity also wanes, and the leadership schisms into parties competing rancorously for votes, but which, with the help of pro-democracy constitutional reforms and culturally-embedded memory, steers wide of the dysfunction that led to Trumpism.
Or, imagine a variation with a Brutus paired to the Caesar, a Camden-raised Secret Service agent on the president's detail. The agent unintentionally overhears the preparation for the nuclear strike just as the order is about to be delivered, and without thinking he shoots and kills the president before it can be made, and is in turn shot and killed instinctively by another agent. The details of the incident are leaked by sources inside the administration, and the domestic and international furor over a democidal nuclear strike being averted by the sacrifice of a lone Secret Service agent forces a reckoning.
The two variations involve the same institutional failures; the country is saved from autocracy (and the people of Camden from annihilation) more or less by luck. One would therefore hope that whatever institutional reforms come out of the first case can also come out of the second. In the first case, though, the destruction leaves no choice but to start fresh (the constitution having been hopelessly mangled). In the second case the universe provides nothing but the wake-up call, and so a different kind of moral courage has to be mustered to rise to the occasion.
The most difficult act of courage demanded is for Democrats to submit to creative destruction and recreation of the structure, leadership, and traditional coalitions of their party. In the same way that, as Linda would be forced to own her part if her marriage fails, she is better off doing so voluntarily in order to reconcile, accepting accountability for its part in the rise of Trumpism and pursuing deep reforms is preferable to waiting for authoritarianism to destroy the party organically. The challenge is then how to select and develop leaders and infrastructure for a proper pro-democracy unity party to pursue the necessary reforms. The painful worst-case-scenario provided a crucible for the new republic's leadership, while narrowly averting it threatens to leave the old guard in place or have their replacements be unworthy, incompetent opportunists.
I should reiterate and emphasize that, among Democratic politicians, "resisting" Trumpism cannot count as a special test of their valor, honor, and patriotism, being only what is been expected of them as Democrats politicking against a Republican. Trumpism has provided an excellent test of pre-MAGA Republicans' honor and patriotism, and proved an overwhelming number of them to be treasonous. From them he exacted a price in a Faustian bargain, treason for power. On the other hand, a number of pre-MAGA Republicans, such as Liz Cheney and Adam Kinzinger, proved their patriotism by resisting Trump and also paying a price. There is simply no evidence for the Democrats pointing in either direction. A principled anti-Trump reformist movement has to be built out from a core of patriots like Cheney and Kinzinger, and others from either party whose loyalty to country and democracy has actually been tested.
But if a deep reckoning and realignment is called for in the scenario of an unhinged Trump almost nuking an American city to permanently seize power, it is arguably also true that the milder version of Trump we actually have is also a matter of luck. It was not preordained that the real Donald Trump would prefer, as he seems to do, cosplay authoritarianism over the real thing (remember the recitations about how it only took Hitler 53 days to destroy democracy in Germany?). Wouldn't it be wise to heed the wake-up call as a very near thing, and seize the enormous opportunity for renewal and much-needed reform?
There is a sad version of the Linda and Mike story in which "the other woman" is a horrible person, an unlovable skank, terrible for Mike in nearly every way, including in her treatment of him. When Linda learns about her she is unable to take her seriously as a threat, only as confirmation of Mike's contemptible bad taste. Mike, on the other hand, while perhaps rationalizing his choice to himself as "wanting someone completely unlike Linda" is subconsciously with the skank because his heart belongs to Linda, and hopes that a symbolic betrayal with a skank will be less hurtful than another more her equal, and more likely to lead to reconciliation.
Trump is the political version of that skank, unlovable and skilled at nothing but inflicting pain. The most reasonable conclusion is not that the median American voter has a slightly sado-masochistic streak that the parties must learn to cater to, but that the American social partnership is in a dysfunctional rut, and a sizable portion of the electorate sees in Trump a painful but temporarily useful instrument for shaking things up and forcing renewal. This, in broad brushstrokes, is what Trump voters, and even Trump himself, have been saying all along.