Tom Miller has just pinpointed the exact moment in the presidential race when, in his opinion, an apparent victory for Donald Trump turned into a commanding lead for Vice President Kamala Harris, which she maintains to this day.
“It was right in my face, but I didn’t notice it at first,” the Northwestern University data scientist told this reporter by phone on Sunday. “I saw this huge increase in Harris’ support on July 31, but I didn’t connect it to Trump’s appearance at the National Association of Black Journalists convention that day. That event, not the debate, which only made things worse for Trump, marked the crucial turning point in the campaign.”
Miller’s election forecast is based not on polls but on the odds for both candidates published on the betting site PredictIt. He considers PredictIt’s odds to be far better than polls reflecting voter preferences that are four to five days old. And because polls typically survey 500 to 1,500 likely voters, they contain a lot of statistical “noise” – hence the wide variability in the numbers published by the various modelers.
PredictIt is the most liquid betting market, averaging around 37,000 contracts per day, Miller said. And because each bettor is subject to an $850 limit, no single bettor or group of high rollers can artificially inflate the odds for one candidate or another.
Trump led before the NABJ debacle
First, Miller’s model assumes that the odds on PredictIt accurately reflect the percentages of voters’ votes. Simply put, a candidate who is given a 55% chance of winning, or who is rated at 55 cents on PredictIt, is likely to receive a similar share of all votes cast. Second, Miller shows that historically, the percentages of voters’ votes closely correspond to the number of electoral votes each candidate receives. This relationship, he found, has remained extremely stable in every race since 1960.
Miller’s homepage, The virtual toutshows a chart showing the share of electoral votes that favor the Democrats, overlaid with the events that have significantly changed the odds, and thus also the fluctuations in the projected election result around the 270 votes needed to win.
Between July 21—the day President Biden dropped out of the campaign and endorsed Harris—and July 27, her vote totals rose significantly, before remaining stagnant for four days in a row.
“She was still well behind the former president and it seemed as if her vote had stagnated,” Miller says.
But then, Miller said, came an earthquake that could well turn into a landslide victory for Harris by November. On July 31, at the NABJ’s annual colloquium, Trump falsely claimed that Harris had changed the way she characterized her ethnicity, questioned her bi-racial background, and accused the vice president of “accidentally becoming black” and of Harris “now wanting to be known as black.”
Although the inflammatory comments sparked outrage in the press and among pundits, virtually no one has called Trump’s NABJ interview the decisive turning point of the election. Miller points out that the PredictIt market went into turmoil that day as bettors switched en masse from Trump to Harris.
“On that last day of July, over 100,000 shares traded, three times the usual number,” he says. “Literally overnight, the election shifted from a Republican to a Democratic lean as Harris rose to over 270. Trump’s statements at the NABJ conference proved to be a complete disaster for his campaign. They had nothing to do with Harris’ actions. The enormous shift was entirely Trump’s doing.”
After the NABJ debacle, Trump partially closed the gap – then came the debate
Miller’s chart shows that Harris’ vote count continued to rise over the next two weeks, peaking just before the Democratic National Convention. But the spectacle in the Windy City itself failed to give her an additional boost. By early September, her vote had fallen slightly. And on September 6, news that Trump’s hush money trial would be delayed until after the election boosted her vote. The day before the debate, he was only slightly behind.
“Although Harris was still leading at this point, the race was almost dead,” says Miller. “It’s notable that most of the jumps in Trump’s numbers came from good news about his legal problems.”
Then the debate in Philadelphia sent Harris’s polling predictions soaring. “That surge was the combined result of the debate and Taylor Swift’s support for Harris,” he says.
As of September 22, PredictIt’s odds suggest Harris’ chances of winning are 56.3% and Trump’s 43.7%. These odds, Miller said, would lead to a landslide victory for the vice president with 43 days to go.
“Big events can change everything, there are wars raging that could affect the outcome of the race, and candidates can make big mistakes,” he warns.
But right now, he says, Harris is way ahead and the polls have not yet caught up with the huge lead that is likely to be emerging – and that lead began to emerge the day Trump made those devastating comments to black journalists and squandered the decisive lead that he was never able to regain.