Prediction Markets Roiled by Shifting Sentiment on Biden and 2024 Race

The last forty-eight hours have brought a flurry of unexpected shifts across the major prediction markets, with Polymarket once again leading in trading volume. Among its top markets is the one asking whether Joe Biden will be the Democratic nominee by election day. That market saw significant turbulence starting late Tuesday evening, when Biden’s chances dipped from 76 percent to just under 68 percent before rebounding slightly to 70 percent. That eight-point swing came in response to increasing chatter online and in the press about mounting party pressure and the president’s health following his recent public appearances. Despite the White House’s insistence that he remains in the race, the volume spike suggests rising doubt among traders.

On PredictIt, the focus remains on the 2024 general election. Donald Trump’s odds of winning the presidency rose sharply from 48 cents to 52 cents on Tuesday morning, in part due to new swing state polling data shared by Emerson College showing Trump leading narrowly in Arizona and holding steady in Pennsylvania. Meanwhile, the market on whether Biden will drop out before the convention surged to 24 cents, the highest it has been this cycle, reflecting a mini-panic that rippled through political newsrooms and social media.

Metaculus, the forecasting platform with a more community-driven model, has been slower to react but still notable. Their forecast for the probability that Biden will be replaced fell slightly from 27 percent to 25 percent, indicating a steadier hand from analysts who may view the political noise as overblown. However, Metaculus’s forecast for the likelihood of AI surpassing human-level performance in video generation by 2026 ticked up from 21 percent to 25 percent after this week’s release of new hyper-realistic synthetic media demos from a leading lab.

The most surprising movement by far came in Polymarket’s “Will a major party replace its nominee before the election” market. That saw a jump of nearly 18 percentage points in just twelve hours, going from 23 percent to 41 percent before stabilizing around 39 percent by midday Wednesday. The confluence of Biden’s debate performance, Trump’s ongoing legal battles, and the volatility of the overall race may be combining to create a truly unsettled political cycle. If the price movement is any indication, traders are beginning to bet on a possible shakeup from one or even both campaigns, unheard of in recent American history this late in the cycle.

One emerging trend across platforms is how prediction markets are becoming faster at responding to social sentiment shifts. Posts going viral on X and Reddit now often precede price movements by only minutes. This speed suggests a growing overlap between retail traders and highly online political observers. While volatility can reflect uncertainty, it may also reveal a sharper edge to crowd psychology, especially in moments of national doubt or media frenzy.

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