Hillary Clinton responded to Donald Trump's performance at the first presidential debate Sept. 27, saying "people can draw their own conclusions." (Video: The Washington Post / Photo: Melina Mara/The Washington Post)

Hillary Clinton moved to capitalize Tuesday on a sharp-edged debate performance that exposed vulnerabilities for Donald Trump, excoriating his values and character in an effort to expand her coalition of women, minorities and young voters.

Trump, meanwhile, scrambled to move his campaign forward. While the Republican nominee insisted that he was not unnerved, he and his advisers grasped at excuses to explain why he did not perform better at the first presidential debate Monday night.

Trump on Tuesday was unrepentant and eager to defend his past, denigrating a former beauty pageant winner whom he targeted as his latest foil and vowing to attack Clinton over her husband’s marital infidelities in their next showdown.

In a country divided over two historically unpopular candidates, Trump’s turn is unlikely to shake his core support. But Democrats said they felt assured that Trump’s hot temperament, scattered demeanor and series of statements that left him exposed to further scrutiny would make it increasingly difficult for him to win over the undecided voters he has been courting, especially moderate white women.

“I look back as a former practitioner and say, ‘Is there anything Donald Trump did to convince somebody who wasn’t in his column to be for him?’ ” said David Plouffe, President Obama’s former campaign manager. “I have a hard time thinking there’s many of those people. I don’t think he lost anybody. But that’s not his challenge now. He’s got to add.”

Clinton was ebullient as she returned to the campaign trail Tuesday in Raleigh, N.C., and strove to keep alive the controversies that marred Trump’s debate performance.

“The real point is about temperament and fitness and qualification to hold the most important, hardest job in the world, and I think people saw last night some very clear differences between us,” Clinton told reporters aboard her campaign plane en route to North Carolina.

Trump did little to change the subject. In a Tuesday morning interview on Fox News Channel, he said debate moderator Lester Holt, the anchor of “NBC Nightly News,” was biased, and the Republican complained about the quality of his microphone. Clinton jabbed him for that, telling reporters, “Anybody who complains about the microphone is not having a good night.”

Trump also disparaged a former Miss Universe pageant winner, Alicia Machado, for her physique. In the debate, Clinton raised Trump’s past comments about the Venezuela-born woman, who was crowned Miss Universe at age 19 in 1996.

“He called this woman ‘Miss Piggy,’ and then he called her ‘Miss Housekeeping,’ because she is Latina,” Clinton said in one of the debate’s more electric exchanges.

The next morning, Trump offered an indignant defense of how he dealt with Machado when he was a partner in the company that owned the Miss Universe contest.

At the Sept. 26 presidential debate, Hillary Clinton knocked Donald Trump for his treatment of former Miss Universe Alicia Machado. Here's what you need to know about Machado. (Monica Akhtar/The Washington Post)

“She was the worst we ever had,” he said on Fox, adding: “She gained a massive amount of weight, and it was a real problem.”

The Clinton campaign sought to advance the story across media platforms, releasing a Web video featuring the beauty queen-turned-actor, now a U.S. citizen who lives in California, and arranging a conference call for reporters with Machado, who described the election as “like a bad dream.”

Like Trump’s feud this summer with the Muslim parents of a dead U.S. soldier, the Machado episode rapidly emerged as a microcosm of the campaign — and a test of whether Trump can expand his support beyond his base of aggrieved white voters, most of them men.

Mike Murphy, a veteran Republican strategist who has been critical of the party’s nominee, said Trump’s comments about Machado were “hugely tone deaf.” The debate overall, he said, was for many Republicans “an ‘Oh, crap’ moment. If you thought he had a spring in his step for the last few weeks and was getting back in the hunt, that’s pretty much gone.”

Few of Trump’s supporters went so far as to crown him the victor. House Speaker Paul D. Ryan (R-Wis.), who has been a weather vane for the Republican leadership during this election season, was supportive though muted at a Tuesday news conference. He told reporters that Trump gave a “unique, Donald Trump response to the status quo.”

“I think he gave a spirited argument,” Ryan said, “and I think he passed a number of thresholds.”

Trump’s backers insisted that the debate would not damage his standing in the close race with Clinton. Rep. Peter T. King (R-N.Y.) said, “As far as the temperament, that’s how he’s been for the last 15 months. It got him to the top. . . . He does have the feistiness that I think 51 percent of the American people will like.”

William J. Bennett, who served in President Ronald Reagan’s Cabinet, said of Trump: “When he loses his temper a little bit, many people see that as passion and as someone who’s engaged in the fight and in what he believes. People forgive that — and a leopard can’t change his spots.”

It will take several days before the political impact of Monday’s debate becomes clear, but many Republicans said they were bracing for Clinton to get a bump in the polls. An estimated 84 million people watched the clash at Hofstra University in Hempstead, N.Y., making it the most-watched presidential debate in history.

The event reverberated around the globe. Former Mexican president Vicente Fox said Trump’s behavior should alarm world leaders because he revealed himself to be “ignorant” and “dangerous.”

“When he speaks about the geoeconomic situation and the geopolitical situation and terrorism, he’s absolutely ignorant, and he’s only provoking us democratic leaders from around the world to reject everything he’s proposing,” Fox, who watched the debate on Mexican television, said in a telephone interview. “He is an imperialistic gringo.”

In the United States, the risk for Trump is that a negative impression sets in on shows such as NBC’s “Saturday Night Live,” on social media and in workplace conversations.

Democrats sought to taunt Trump on his uneven performance, particularly given his regular attacks on Clinton’s “stamina” and appearance.

“He seemed unable to handle that big stage, and I really did feel that by the end, with the kind of snorting, the water gulping and the leaning on the lectern, that he just seemed really out of gas,” said Clinton campaign chairman John Podesta.

Trump previewed an even more combative second debate, Oct. 9 in St. Louis, by saying he might “hit her harder,” perhaps over former president Bill Clinton’s affairs.

“I really eased up because I didn’t want to hurt anyone’s feelings,” Trump said on Fox, saying he would have brought up “the many affairs that Bill Clinton had” but held back because the Clintons’ daughter, Chelsea, was in the audience.

“I didn’t think it was worth the shot,” he said. “I didn’t think it was nice.”

Hillary Clinton shrugged off the threat, telling reporters: “He can run his campaign however he chooses. I will continue to talk about what I want to do for the American people.”

Clinton campaigned at a community college gymnasium in Raleigh to whoops and loud applause. “One down, two to go,” she said of the debates.

During a campaign rally in Melbourne, Fla., Tuesday evening, Trump said that Clinton is “a woman that I think is virtually incompetent, certainly as secretary of state.” He called her incompetent repeatedly throughout the rally.

“We’re going to get rid of that crooked woman. She’s a crooked woman. She’s a very, very dishonest woman,” Trump said.

For Democrats, Trump provided what Plouffe called “an embarrassment of riches” at the debate — a series of controversial statements and unresolved, damaging questions. He seemed to affirm that he paid no income taxes; he made side remarks and pained expressions while Clinton praised the vibrancy of African Americans; he said it was a smart business strategy to profit from the housing crash.

Vice President Biden seized on that last point at a rally for Clinton in Philadelphia, where he charged that Trump has no “moral center.”

“This is a guy who said it was good business for him to see the housing market fail,” Biden said. “What in the hell is he talking about?”

Clinton and a brigade of high-profile surrogates plan to continue using Trump’s debate comments against him. She will campaign in New Hampshire on Wednesday with Sen. Bernie Sanders (I-Vt.), hoping to energize young voters there with a discussion of college affordability, while first lady Michelle Obama will stump across Pennsylvania on Thursday.

“He put a lot on the table — a lot of things that are not true and a lot of views that we think are counter to where most voters are,” said Jennifer Palmieri, Clinton’s communications director. “It won’t end tomorrow. There’s a lot that will live on from this debate.”

Anne Gearan in Raleigh, N.C., Jenna Johnson in Melbourne, Fla., and Jose DelReal in Washington contributed to this report.