How has the switch from Biden to Harris changed the presidential race?

President Joe Biden’s decision to not to seek reelection and the remarkably quick unification of Democrats around Vice President Harris as their presidential candidate has transformed the election. But in what respects, and by how much?

One thing is clear: The mood of most Democrats has changed abruptly. Before Biden withdrew from the race, they had resigned themselves to defeat at the presidential level and were shifting their attention to retaining control of the Senate and regaining it in the House. When Harris emerged as Biden’s replacement, hope replaced despair, contributions flowed in at a record rate, and offers to volunteer for the campaign surged. Only a third of Biden’s backers said that they would cast their votes to express support for him, while nearly two-thirds said that they would do so to oppose Donald Trump. By contrast, half of Harris’ backers said that their vote would be an affirmative expression of support.

The shift in the polls has been less dramatic than the shift in the mood. In the surveys conducted shortly before Biden’s withdrawal, Trump led in the national race by an average of 2.5 percentage points. In surveys conducted by ten polling organizations during the week following Biden’s withdrawal, Trump’s lead against Harris averaged 1.2 points. Not enough state polls have appeared yet to assess changes in the swing states with any confidence.

Some pundits are asking whether Harris is on her way towards reassembling the Obama coalition. A more pertinent question is whether she can reassemble the coalition that enabled Biden to do in 2020 what Hillary Clinton could not quite get done in 2016. To assess this issue, Table One compares the results of the recent NYT/Siena poll with the Pew Research Center’s validated voter study of the 2020 contest.

This comparison suggests a few tentative conclusions.

First, there is no reason to regard 46% to 47% of the popular vote as a ceiling on Trump’s share in 2024. In the surveys conducted during the past week, he has averaged 47.7%. The real question is whether Harris can narrow the gap between her current 46.5% average and the outright majority she will need to have a chance of prevailing in the Electoral College. After all, Biden’s 4.5-point margin in the national popular vote was just barely enough to give him an Electoral College majority. Even if some of Trump’s gains have come in states (such as New York) that he has no chance of winning, Harris will still need to improve on her current standing by at least four points—a daunting but not impossible task.

Second, gender could turn out to be one of the driving forces this year. While Harris is doing no better among women than Biden did in 2020, she is running 11 points behind him among men. She cannot win with only 37% of the male vote—unless she can engineer offsetting gains among women.

Third, Joe Biden reversed Hillary Clinton’s losses in the “Blue Wall” states (Wisconsin, Michigan, and Pennsylvania) by increasing Democrats’ share of the white working-class vote from 28% in 2016 to 33% in 2020. As of now, Harris stands at just 28% among these voters, not enough to win—unless she achieves a massive mobilization of white college-educated and non-white voters.

She has her work cut out for her. She is doing no better among white college-educated voters and Hispanics than Biden did four years ago, and astonishingly, she is doing much worse among African Americans. In 2020, Biden received 92% of their vote, statistically identical to Clinton’s 91% in 2016. But now, according to the NYT/Siena poll, Harris is garnering only 69%, while Trump has tripled his share from eight percent in 2020 to 23% now.

Five surveys during the past week have published group-by-group breakdowns of the overall vote¹, and Trump’s share of the African American vote has averaged 22%. Still, these results must be regarded with caution because the results have ranged from a high of 34% to a low of 11%. It is too early to say that a fundamental realignment is underway in the heart of the Democratic base.

In sum, Harris has a chance, which Biden did not after his disastrous debate with Trump rippled through the Democratic electorate and party leaders. But despite the party’s surge of enthusiasm, Harris begins her race for the presidency as an underdog. To prevail, she will need a strong offense against Trump, coupled with an effective defense against the Republican attacks that have barely begun.