Perhaps this series by Ben Hunt will help you decide if there is enough centre to support a centrist. I doubt it. https://www.epsilontheory.com/things-fall-apart-pt-1/
Would you need to do anything super fancy to beat the market? You could in thoery just find 100 median voters who swap parties, tell them both Trump and the newcomer are pedophiles to simulate attack ads and ask who they would vote for after giving them an entire minute to think about it(to simulate the months of them hearing about it). Repeat for each canidate.
Alternatively you could check polling numbers for swing States to filter out the noise of who wins calinforna for free.
The public debate for who should be the Democratic Party presidential candidate for the 2020 electoral race hinges on whether the Dems are likelier to win by nominating a progressive or socialist, or by nominating a centrist or moderate. Assuming this is a problem one wanted to approach epistemically (as opposed to just viewing the debate as a power struggle), we should look for facts of the matter about whether, overall, Americans are likelier to elect a progressive/socialist, or moderate/centrist to the Presidency in 2020. Unfortunately there is no apparent consensus about how to make traction on this problem.
commonly regarded as the most moderate/centrist prospective Dem nominees, to Bernie Sanders, whose policy platform is generally furthest to the left among the lot of them. Leading the pack is Kamala Harris who has announced her presidential run and is perceived as somewhere between centrist Dems and democratic socialists like Sanders, with Sanders and Biden tied for 2nd (both are yet to publicly declare if they'll be running in 2020). PredictIt's predictions for which candidate will fare best are strongly correlated with who is regarded as being the strongest contender as a personality. They appear to have little to no correlation with the candidate's perceived ideology. The high level of apparent uncertainty in the predictions is likely an artifact of it being so early in the presidential race, as opposed to the prediction markets pricing in how likely the candidates' policy platforms are to appeal to the median voter.
In other words, if there is solid info out there which could best predict whether, in general, a leftist or centrist Democrat is likelier to win the Democratic nomination and/or the Presidency in 2020, it doesn't look like this has been priced into PredictIt's predictions yet. So to answer this question, we might have to find info prediction markets haven't yet, or that they may have at least overlooked.
Suggestions for how to answer this question: