"It’s gone from a drastic landslide in Trump’s direction to a drastic landslide for Harris," Miller said of his forecasting model.

Even prior to the June debate between Trump and President Joe Biden — which was widely viewed as the catalyst for Biden's eventual exit from the 2024 race — Miller's metrics predicted a staggering defeat for Biden. He forecasted that Trump could win as many as 400 Electoral College votes prior to Biden's disastrous debate performance, which went as high as nearly 500 electoral votes.

But after Biden dropped out and endorsed Harris — prompting a surge of excitement from the Democratic base and hundreds of millions of dollars in new fundraising — the odds flipped in the vice president's favor in just a few weeks. Despite Trump catching up to Harris in the wake of the Democratic National Convention and getting back into a virtual tie with the vice president, Harris blew past him once again after last week's debate, which was viewed by 67 million Americans.

"Within a day after the candidates left the podium, Harris had jumped to exactly over 400 electoral votes," Fortune's Shawn Tully wrote. "The Harris endorsement from Taylor Swift, secured the day of the debate, probably helped sink Trump’s chances, according to Miller. Since then, Harris has maintained [her] 400-plus vote total."

The most hotly contested battleground states — which include Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin — will ultimately decide which candidate crosses the 270-vote threshold. Miller is predicting a clean sweep for Harris in all of them.

“We’re talking about a blowout where Harris gets over 400 electoral votes and wins Michigan, Pennsylvania, North Carolina and every other swing state," he said.

Miller based his model around betting trends on PredictIt, which is the largest betting market for U.S. politics. Tully explained that Miller "took the Predictit odds in the 56 individual voting jurisdictions, tracked the hourly changes, and used his proprietary model to roll the data into daily odds." Miller said he viewed PredictIt as more accurate than traditional polling, which uses a much smaller sample and is typically a week behind current trends.

" “You have tens of thousands of people betting on the site at all times of the day,” Miller told Tully. “The maximum contract is $850, and 37,000 ‘shares’ are traded on average every day.”

"“Financial markets are forward-looking, and incorporate information instantaneously, and Predictit provides the same benefits,” he added.