Will Harris’s Lead Last? A Few Questions That Will Shape the Answer.

Kamala Harris has wrapped up an extraordinary month.

In that short time, she’s completely transformed the 2024 presidential election. She leads in most national and battleground state polls, and the real-world signs of the enthusiasm for her candidacy are everywhere, from filled-up stadiums to record-setting campaign contributions.

All this was hard to imagine before President Biden dropped out, when a majority of Americans had an unfavorable view of her. Her previous run for president did not go well. If anything, her record in national politics saddled her with considerable baggage, including a high-profile role on immigration policy in the Biden administration and a series of unpopular policy pronouncements in her last presidential campaign.

But Vice President Harris turned around her fortunes anyway — and quickly. Clearly, many Americans did not have a strong view of her, and after a month of well-delivered speeches and upbeat appearances in the national spotlight, she has successfully reintroduced herself to the country. Now, more battleground state voters say they have a favorable than unfavorable view of her — no small feat in a jaded and divided country.

But this extraordinary turnaround wasn’t just about Ms. Harris. It was also about voters’ immense dissatisfaction with a Biden-Trump rematch, which had brought anxiety and dismay to millions. In an instant, Ms. Harris’s candidacy offered these voters what they had been yearning for: something new, different and more hopeful than that dreaded rematch. It uncorked years of pent-up Democratic enthusiasm. It let Ms. Harris bring the joy back.

As a result, she has become a certain kind of change candidate. No, she doesn’t represent a change in policy or party, but she represents the promise of a new beginning. She has also turned Donald J. Trump into a something like a candidate of the status quo, or even the past — not the policy status quo, but the candidate of a contentious and exhausting decade of American political life.

It was enough to give Ms. Harris a lead heading into her convention. If history is any indication, her edge could expand further in the next wave of polls, taken after tens of millions watched her nationally televised address.