Democrat Hillary Clinton exchanged sharp blows with Republican Donald Trump in the first debate of the presidential candidates Monday, with her hitting him on his refusal to release his income taxes, promoting the “birther” controversy and filing multiple bankruptcies.

Trump struck back, depicting her as a “typical politician” with few accomplishments over two decades. He said that she would hike taxes and regulate companies out of business and that she failed to stem terrorism during her tenure as secretary of state.

Trump started out the widely anticipated faceoff at Hofstra University by interjecting and talking over Clinton. But the candidate, whose assertive style marked the Republican primary debates, was more on the defensive in the second half of the debate.

Over the course of about 100 minutes, the candidates — locked in an extremely tight race with an unusually high number of undecided voters — traded hard knocks over the Middle East, tax plans, guns and presidential temperament. Clinton used the word “racist,” more than once, to describe his behavior.

Clinton especially targeted Trump’s refusal to release his income taxes, breaking a presidential candidate tradition. That led to a sharp exchange.

“So you’ve got to ask yourself why?” Clinton said. “Maybe he’s not as rich as he says he is. Maybe he doesn’t give as much to charity as he says. . . . Or doesn’t want us to know he paid nothing in federal income taxes.”

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She noted Trump, when filing to open a casino in the 1980s, filed a statement saying he didn’t pay any taxes that specific year.

“That makes me smart,” Trump interrupted.

“It must be something. Maybe even something terrible he’s trying to hide,” Clinton said.

Trump said he couldn’t release his taxes because he’s being audited — the moderator, NBC’s Lester Holt, pointed out that he could — then pivoted to say he’d release his returns when she released emails she deleted while serving as secretary of state.

Clinton said the emails were a mistake. Trump countered it was deliberate.

But Clinton swung back on the offensive, saying Trump’s business record was faulty — and marked by multiple bankruptcies and “people you have stiffed.” She also referenced his wealthy father, implying that Trump had the kind of advantages others don’t.

“Donald was very fortunate in his life,” she said — she addressed him by his first name throughout the night. “He started his business with $14 million, borrowed from his father.”

“My father gave me a very small loan in 1975,” Trump said (he’s said previously it was closer to $1 million), “and I built it into a company that’s worth many, many billions of dollars.”

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Trump acknowledged that on “occasion, four times, we used certain laws that are there . . . we were taking advantage of the laws of the nation” in seeking bankruptcy protection.

As the race moves into the final six weeks, the two candidates are running almost even, according to the consensus of national polls. Somewhat predictably, Trump surged after the Republican convention, Clinton after the Democratic. And now it is leveling out again.

Heading into the debate, Clinton had an average 1.5 percentage-point lead, according to FiveThirtyEight.com, a 2 percentage-point lead according to Real Clear Politics. But that’s down from a 7-point lead a month ago.

The striking figure within the polls is the large number of undecided voters — especially compared with 2012. Roughly 15 percent to 18 percent of the electorate still has not picked either Clinton or Trump — that compares with about 6 percent four years ago when President Barack Obama battled Republican Mitt Romney.

Clinton seemed to reach out to the undecided voters when she brought up the temperament issue. She cited his use of blistering statements on Twitter and his “cavalier attitude about nuclear weapons.”

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“A man who can be provoked by a tweet should not have his hands anywhere near the nuclear codes,” Clinton said.

Trump replied that temperament was his “strongest asset.”

“I have much better judgment than she does,” Trump said. “I also have a much better temperament than she does . . . I think my strongest asset is my temperament, by far. I think I have a winning temperament.”

Trump criticized Clinton as a “typical politician” who has been promising changes for decades, especially on foreign-trade agreements. Trump’s vow to reopen such agreements and bring manufacturers back to the United States was a major theme in his push for the GOP nomination.

“She’s been doing this for 30 years and why hasn’t she made the agreement any better?” Trump said, earlier on in the debate when he was more aggressive. “Secretary Clinton and other politicians should have been doing this for years, not just right now because we have created a movement.”

Later, when the Democrat said she had a plan to help small businesses and hold foreign nations to trade terms, Trump sought to dismiss it: “Typical politician. All talk, no action. Sounds good, doesn’t work. Never going to work.”

Clinton took Trump to task for pushing the false idea that President Barack Obama wasn’t born in the United States — the so-called birther controversy. The Republican tried to say Clinton’s campaign promoted the idea in 2008, which many sources have refuted.

Trump refused to back down.

“I got him to give the birth certificate,” Trump said.

Asked by Holt what he’d say to people who think that it was racist to raise the issue about the nation’s first African-American president, Trump replied: “I say nothing. Because I got him to produce it. I say nothing. I did a great service for the country.”

Afterward, Trump said he had information that would hurt Clinton and her family that supporters wanted him to use.

“But it wouldn’t be nice,” he said. “I’m very happy I didn’t mention Bill’s indiscretions,” he told reporters, referring to the former president. But he said it wasn’t out of bounds and he may bring it up in the next debate because of the nasty ads she has aired.