Harris will lose – unpopular and voters want change.

At the outset, one enormous caveat is necessary: Ms. Harris became a candidate for president only on Sunday. She will have every opportunity to reintroduce herself to the nation, distinguish herself from Mr. Biden and rally Democratic voters in the weeks ahead. Similarly, her opposition will have every opportunity to criticize her handling of the border or her support for a ban on fracking or for Medicare for All. In the end, her standing could easily change for the better — or worse.

But a majority of voters have long had an unfavorable view of her. She has trailed Mr. Trump in nearly every national and battleground state poll conducted so far this year. In the most recent New York Times/Siena College poll of Pennsylvania, just 42 percent of likely voters said they viewed Ms. Harris favorably — well short of the 51 percent who had a favorable view of Mr. Biden in the state ahead of the 2020 election. It’s even lower than the 46 percent who said the same for Mr. Trump in the recent poll.

With numbers like these, a Harris-Trump matchup doesn’t look much like the 2020 presidential election, when Mr. Biden prevailed as a moderate candidate who was liked by a majority of voters. Instead, it’s more like the Biden-Trump contest of a month ago, before the debate, when Mr. Trump led narrowly and the race seemed poised to be decided by the fickle voters who dislike both candidates — the so-called double haters.

A year ago, many Democrats weren’t alarmed by the prospect of running an unpopular candidate like Mr. Biden (or presumably Ms. Harris) against Mr. Trump. Back then, many asserted that America had an anti-MAGA majority; in this view, it was all but impossible for Mr. Trump to win the presidency, despite Mr. Biden’s poor job approval ratings. As late as this spring, Mr. Biden’s team comforted itself with the assumption that the election would ultimately be about democracy and therefore he would prevail, despite his obvious liabilities.

In the end, Ms. Harris and the Democrats might win a coin-flip election by campaigning on abortion and democracy, just as Mr. Biden’s advocates hoped he would. But it’s far harder to be confident about that assumption today. After all, Mr. Biden had been trailing in the polls for essentially 10 straight months — long before the first presidential debate.

The polls have offered a long list of explanations for his weakness, and many of them had nothing to do with his age. A majority of voters have said the country is heading in the wrong direction. They have said the economic and political system in the country is broken. They’re deeply concerned about the economy and immigration — two of Mr. Trump’s strongest issues in surveys. In poll after poll, voters say they’re looking for change.