https://electionbettingodds.com/President2020_week.html
Nate Silver has Biden as a 3:1 favorite but the markets have Biden favored at a slight coin flip (53 to 43). Markets could be factoring the '2016 shell shock factor' (that the polls could be wrong again) as well as Trump going to any lengths to win (voter suppression, kneecapping the post office, etc).
Note that the betting markets are not necessarily predictive in big races, as they were completely wrong in 2012(had Romney over Obama), in 2016 (Hilary was up to 87cents the day before election day), and this year in the primaries (thought Bloomberg would win, thought Bernie would win), and for the VP pick (Susan Rice was way ahead on the day Harris was chosen).
RW white guys with disposable income heavily dominate betting action, thus their viewpoint is reflected. Regardless of what some say, it's impossible to separate worldview from betting especially in a presidential race in such a polarized environment. The Russians and others could also be pumping money into the market to make things look better for Trump.
Even Nate Silver has said betting markets are not predictive.
https://twitter.com/NateSilver538/status/1199372917777346565
https://fivethirtyeight.com/features/oct-23-the-virtues-and-vices-of-election-prediction-markets/
Markets of any kind are potentially subject to herding behavior. Even if the “rogue trader” does not have superior information about the campaign, other traders might alter their behavior assuming that he did.
Or traders could be betting on speculation – buying up Mr. Romney’s stock, for example, in the hope of selling it at a higher price later, even if that price diverged from their estimate of the “fundamentals” in the race.
Coming up with a probabilistic assessment of the chances of each candidate’s winning the Electoral College is intrinsically a very challenging task. ”Gut-feel” probability estimates are not likely to be much good. It is the sort of problem, in my view, that benefits from a more rigorous approach, i.e. building a model. Yet, models are constrained by the lack of historical data and the infrequency of presidential elections – only since about 1980 has state-by-state polling of the election been common.
In these circumstances, traders may be looking for an anchor to calibrate their assessment of the probabilities. It is certainly possible that FiveThirtyEight itself serves something of this function.
The FiveThirtyEight model is sometimes perceived as being incredibly bold for having Mr. Obama as a two-to-one favorite despite what is certainly very close polling, but the few other models that seek to frame the election in probabilistic terms tend to give Mr. Obama an even clearer advantage, putting his odds at between 80 and 95 percent.