A new poll conducted after President Biden’s dismal debate performance shows New Hampshire is now in play — and President Trump has a slight lead.

The Saint Anselm College poll released Monday shows Trump with a two-point lead over Mr. Biden in the Granite State, which hasn’t voted Republican in a presidential election in nearly a quarter-century.

This is the latest sign of trouble for the Biden campaign, as calls for him to bow out of the race grow louder — even from within his own party — after he stumbled putting together compete sentences in the debate with Trump last week. A CBS poll released over the weekend finds that 72 percent of Americans think Mr. Biden doesn’t have the mental or cognitive health to serve as president.

“This was a five-alarm fire,” a Republican strategist, Matthew Bartlett, tells the Sun. “If Watergate was a constitutional crisis, this is clearly a capability crisis.”

Trump’s lead in the Saint Anslem poll is within the 2.3 percent margin of error, but it shows Trump gaining ground in a state he lost to Mr. Biden by more than 7 percentage points in 2020. Trump narrowly lost the state to Secretary Clinton in 2016.

The survey sampled 1,746 New Hampshire registered voters on June 28 and 29 — the two days after the debate. Granite Staters surveyed overwhelmingly said Trump won the debate, and 19 percent said the debate would affect their vote.

“After a remarkable six months that saw him swiftly dispatch his primary rivals and become the first former President to be convicted of a felony, Donald Trump has erased a 10-point polling deficit and now leads President Joe Biden by a narrow 2-point margin,” the director of the New Hampshire Institute of Politics, Neil Levesque, said in a statement.

He added, though, that “with 17 percent of voters having an unfavorable opinion of both candidates, this race is likely to remain volatile all the way to the finish.”

New Hampshire is considered a swing state, though not in presidential elections. Mr. Biden and his surrogates have made several trips to New Hampshire in recent months, indicating they have been concerned about retaining the state’s four electoral votes since before last week’s debate.

In another sign of worry, none of the state’s Democratic candidates for governor or congress have released statements in support of Mr. Biden since last week’s debate. The chairman of the New Hampshire Democratic Party did not return the Sun’s request for comment.

Mr. Bartlett says the state is absolutely in play this year. He says moving South Carolina’s Democratic primary ahead of New Hampshire’s was “an unforced error,” but he says Mr. Biden’s “big mistake was clearly the choice to run.”

Mr. Biden spent the weekend at Camp David with his family, where they reportedly discussed his presidential campaign. The first lady and Hunter Biden are the key players pushing for Mr. Biden to stay in the race, according to the New York Times.

Mr. Biden’s surrogates are pointing to his two public appearances since the debate that show the president to be coherent and energized. His critics, though, dismiss these, saying it’s easy to read from a teleprompter and take no questions from the press.

“For the good of the country, he should step down,” the chairman of the New Hampshire Republican Party, Chris Ager, tells the Sun. “Now the whole world knows what we’ve known for a long time: that he’s just not capable. I’m worried about an adversary trying to take advantage of that weakness.”

Mr. Ager says Mr. Biden may be an easier candidate for Trump to beat in November than a younger replacement, but he says the risk to the country is too great to hope that Mr. Biden stays in.

“This wasn’t just a bad day,” Mr. Ager says. “You have one or two opportunities to be in front of the whole country debating your opponent and you can’t be ready for that, then what happens in the middle of a really important cabinet meeting where you have to decide between war and peace?”