President Biden has nearly erased Donald J. Trump’s early polling advantage, amid signs that the Democratic base has begun to coalesce behind the president despite lingering doubts about the direction of the country, the economy and his age, according to a new survey by The New York Times and Siena College.

Mr. Biden and Mr. Trump are now virtually tied, with Mr. Trump holding a 46 percent to 45 percent edge. That is an improvement for Mr. Biden from late February, when Mr. Trump had a sturdier 48 percent to 43 percent lead just before he became the presumptive Republican nominee.

Mr. Biden’s tick upward appears to stem largely from his improved standing among traditional Democratic voters — he is winning a greater share of voters who supported him in 2020 than he did a month ago. Then, Mr. Trump had secured the support of far more of his past voters compared with the president — 97 percent to 83 percent — but that margin has narrowed. Mr. Biden is now winning 89 percent of his 2020 supporters compared with 94 percent for Mr. Trump.

The tightening poll results are the latest evidence of a 2024 contest that both campaigns are preparing to be excruciatingly close. The last two presidential elections were decided by tens of thousands of votes in a handful of battleground states, and this one could be just as tight. In a nation so evenly divided, even the tiniest of shifts in support could prove decisive.

Beneath the narrowing contest, many of the fundamentals of the race appear largely unchanged.

The share of voters who view the nation as headed in the wrong direction remains a high 64 percent. Almost 80 percent of voters still rate the nation’s economic conditions as fair or poor, including a majority of Democrats. And both Mr. Biden and Mr. Trump remain unpopular, for familiar reasons. Most voters think Mr. Biden is too old. A majority believe Mr. Trump has committed serious federal crimes.

“Just blah,” said Beth Prevost, a 59-year-old hairdresser and independent voter in Windsor Locks, Conn., summing up the feelings of so many about the rematch. She said she was leaning toward Mr. Biden as “the lesser of the two evils.”

“You can recover from bad policies, but you can’t recover from a bad heart,” Ms. Prevost said. “And Donald Trump has a bad heart.”

The survey comes just before Mr. Trump’s history-making criminal trial in New York City, the first for a former American president. He faces charges related to falsifying records related to a hush-money payment to a porn star. The case is one of four involving felony indictments against Mr. Trump, but it is the only one so far with a trial set to begin before the election.

Yet despite the potential for the Republican nominee to face jail time, only one in four voters said they were yet paying very close attention to the former president’s legal travails.

The Biden campaign, which has already begun advertising in battleground states, has hoped the reality of a potential second Trump term will snap reluctant Democrats back toward their typical partisan posture. There is some initial evidence of that happening.

In the last month, Mr. Biden’s support among white voters remained flat, but it has inched upward among Black and Latino voters, even if it still lags behind traditional levels of Democratic support. Mr. Biden was faring better than he had been a month ago in suburbs and among women, though he was weaker among men. Younger voters remain a persistent weakness, while older voters provide a source of relative strength for the Democratic president.

The poll’s overall margin of error was 3.3 percent. But the results among subgroups are less statistically reliable because there are fewer respondents in them. Still, this poll showed Mr. Biden with his strongest performance among nonwhite voters among the last three Times/Siena surveys since December.

Age, however, remains a political albatross for Mr. Biden.

A full 69 percent of voters still see the 81-year-old Democrat as too old to be an effective president. Mr. Trump, who turns 78 in June, would also be the oldest president in American history if elected. But voters do not have the same doubts about his capacity to serve, with only 41 percent viewing him as too old.

There was one notable shift in the last month. Among voters who are over 65, the share who view Mr. Biden as too old has dropped significantly.

Russell Wood, 67, a Democratic retiree and a veteran who lives in Los Angeles County, said he had noticed a marked change in Mr. Biden’s energy levels. He was disappointed Mr. Biden had skipped the traditional pre-Super Bowl interview but was pleased with the performance he had seen since.

“He did a really great job at the State of the Union, and since then it’s like he’s been a different Joe Biden,” Mr. Wood said, adding: “I know he’s on the campaign trail day in and day out. I have no complaints there.”

The economy also continues to be a drag for the president, who has tried to frame his “bottom up and middle out” job agenda under the banner of “Bidenomics.” Young voters are especially sour, with more than 85 percent rating the economy poor or fair.

Voters in the poll gave Mr. Trump’s and Mr. Biden’s handling of the economy almost perfectly inverted ratings: 64 percent approved of Mr. Trump’s handling of the issue as president and 63 percent disapprove of Mr. Biden’s job on the issue now.

Immigration gave Mr. Trump his other biggest edge among a host of issues voters were asked about in the survey. Border crossings hit record highs at the end of last year. A slim majority approved of Mr. Trump’s handling of immigration as president, while 64 percent of voters disapproved of Mr. Biden’s job on those matters.

Luis Campino, a 50-year-old independent voter who immigrated from Colombia and now lives in Highland, N.Y., said there were “dangerous” people crossing the border. “They’re coming in like nothing,” he added.

Mr. Campino said he had voted for Mr. Biden in 2020 but was planning to vote for Mr. Trump as the “lesser of the evils,” a decision driven in part by his concerns about crime and immigration.

In the poll, Mr. Biden was given better ratings than Mr. Trump on his ability to unite the nation and his handling of both race relations and the pandemic.

But with the war in Ukraine dragging into its second year after Russia’s invasion and the civilian death toll rising in Gaza after Israel’s assault after the terror attack by Hamas, voters gave Mr. Trump significantly higher marks on his handling of foreign conflicts.

Only 36 percent approve of Mr. Biden’s managing of those conflicts, with especially glaring weaknesses among younger voters. Only 4 percent of voters under 45 strongly approve of his job on such international matters.

Danny Ghoghas, 23, a bartender and server who lives in Burbank, Calif., is strongly considering staying home on Election Day to protest Mr. Biden’s response to the conflict in Gaza.

“I really don’t like Donald Trump and would not like him to be in office again,” said Mr. Ghoghas, a Democrat. “That’s why I would vote for Biden again. But other than that, I can’t really think of a good reason to vote for him.”

The generational differences on foreign affairs were notable. While voters of all ages viewed Mr. Trump similarly, Mr. Biden received far worse ratings from voters under 45, 70 percent of whom disapproved. Among those who are 45 and older, a slimmer 53 percent majority disapproved.

Mr. Biden has made Mr. Trump’s potential to undermine democratic rule after the riot of Jan. 6, 2021, a centerpiece of his re-election campaign. But so far, equal 31 percent segments of respondents said that Mr. Biden and Mr. Trump were “good for democracy.” The number who said Mr. Trump was “bad for democracy,” 45 percent, only slightly outpaced those who said the same of Mr. Biden.

Also in the poll, nearly equal shares of voters labeled Mr. Trump and Mr. Biden a “risky choice” for the country.

The survey did not ask about potential third-party candidates. But roughly 5 percent of voters seemingly unhappy with the Trump-Biden choice volunteered the names of other candidates they planned to vote for, including Robert F. Kennedy Jr., the Democrat-turned-independent who is battling to get on ballots nationwide.

It is not clear yet what effect the looming criminal trial will have for Mr. Trump, with 37 percent saying they were paying little to no attention at all.

Still, a 58 percent majority of voters view the charges that he falsified business records to cover up hush money payments made to the porn star Stormy Daniels as either very serious or somewhat serious. Opinions fractured predictably along partisan lines, though a majority of independents notably view the charges as at least somewhat serious.

More interesting was the gender gap on that question.

Women were twice as likely as men, 40 percent to 20 percent, to see the charges related to the porn star as very serious; men were twice as likely as women to see the charges as not serious at all, 30 percent to 15 percent.

Ruth Igielnik, Alyce McFadden and Camille Baker contributed reporting.

Here are the key things to know about how this Times/Siena poll was conducted:

• We spoke with 1,059 registered voters from April 7 to 11, 2024.

• Our polls are conducted by telephone, using live interviewers, in both English and Spanish. More than 95 percent of respondents were contacted on a cellphone for this poll.

• Voters are selected for the survey from a list of registered voters. The list contains information on the demographic characteristics of every registered voter, allowing us to make sure we reach the right number of voters of each party, race and region. For this poll, we placed nearly 127,000 calls to more than 93,000 voters.

• To further ensure that the results reflect the entire voting population, not just those willing to take a poll, we give more weight to respondents from demographic groups underrepresented among survey respondents, like people without a college degree. You can see more information about the characteristics of our respondents and the weighted sample on the methodology page, under “Composition of the Sample.”

• The poll’s margin of sampling error among registered voters is plus or minus 3.3 percentage points. In theory, this means that the results should reflect the views of the overall population most of the time, though many other challenges create additional sources of error. When computing the difference between two values — such as a candidate’s lead in a race — the margin of error is twice as large.

You can see full results and a detailed methodology here. If you want to read more about how and why we conduct our polls, you can see answers to frequently asked questions and submit your own questions here.