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Donald Trump and Hillary Clinton, in a fiery opening debate where seemingly nothing was off limits, clashed sharply Monday night as the Republican nominee worked to cast his rival as a career politician unable to bring change – and the Democratic nominee fought to tag Trump as an empty suit “hiding” something from the American public.

Entering their first encounter after a solid week of intense preparation, Clinton seemed ready for several of Trump’s taunts on stage at Hofstra University.

When Trump, discussing how he’d been “all over” the country talking to inner-city communities, said, “You decided to stay home, and that’s okay” – Clinton had a swift retort.

“I think Donald just criticized me for preparing for this debate. And yes, I did,” Clinton said. “And you know what else I prepared for? I prepared to be president, and I think that’s a good thing.”

Later in the debate, Trump summed up his counter-argument in a few words: “Hillary has experience, but it’s bad experience.”

The debate took a number of twists and turns, and it’s unclear how and whether it will tilt the race at a time when the polls are tightening. The general election rivals will meet twice more on the debate stage next month.

Despite some expectation-setting in the run-up to Monday’s face-off that the candidates would bring a reserved demeanor, the niceties did not last long. Trump and Clinton clashed early and often and rarely did they dial back the tensions.

Trump, toward the close of the debate, tried to undermine Clinton’s persistent argument that he’s temperamentally unfit for the nation’s highest office.

“I have a winning temperament. I know how to win,” Trump said, before contrasting that against Clinton’s widely mocked video-conference address last week to a labor union. Trump told Clinton “you were totally out of control.”

She countered: “A man who can be provoked by a tweet should not have his fingers anywhere near the nuclear codes.”

Trump also repeated his charge that Clinton “doesn’t have the stamina,” while Clinton responded by reviewing her secretary of state resume.

“As soon as he travels to 112 countries and negotiates a peace deal, a cease fire, release of dissidents … or even spends 11 hours testifying before a congressional committee, he can talk to me about stamina,” she said.

Trump used the debate to hammer campaign themes like calling for a return to “law and order” and vowing to bring jobs back to America. Clinton focused on rebuilding middle-class America as well.

But in between, the debate veered into personal shots.

Trump reached back to the 1990s to hammer her former president husband Bill Clinton over NAFTA, which he called “the worst trade deal maybe ever signed anywhere,” and remind voters about her controversial comment from that era referring to some young criminals as “super predators.”

Clinton, though, had a sharp exchange with Trump as she challenged him to release his tax returns, which Trump has said he can’t do because of an audit.

Clinton questioned whether Trump is really as wealthy as he claims and said, “There’s something he’s hiding.”

Trump issued Clinton a challenge of his own, saying he’ll defy his lawyers’ advice and release his taxes if she releases the “33,000 emails” she erased.

“As soon as she releases them, I will release my tax returns,” Trump said.

The tone of the debate seemed to get more caustic as the debate neared its end.

Clinton said of Trump, “This is a man who has called women pigs, slobs and dogs.”

And they traded shots over Trump’s role in questioning President Obama’s birthplace. Clinton said he peddled a “racist lie,” while Trump said Clinton aides played a role as well.

“When you try to act holier than thou, it really doesn’t work,” he said.

The debate was moderated by Lester Holt, who stayed out of the fray initially but toward the end challenged Trump on a handful of assertions including his claim he opposed the Iraq war.

At one point, Trump also accused Clinton of “fighting ISIS your entire adult life,” and she later mocked him for blaming her for “everything” and saying what she described as “crazy things.”

The Democratic nominee also ripped Trump over his tax plan, which she said would “blow up the debt” while mainly benefiting the wealthy.

“I call it trumped-up trickle down,” she said. “That is not how we grow the economy.”

Trump, meanwhile, described Clinton as late-to-the-game when it comes to scrutinizing American trade deals.

“Secretary Clinton and others … should have been doing this for years, not right now,” he said.

He said he wanted to keep jobs and business in the United States by threatening to tax companies that move jobs outside the U.S. He told Clinton pointedly, “You’ve been doing this for 30 years. … I will bring back jobs. You can’t bring back jobs.”

He made a similar argument about her ability to take on the Islamic State.

“You were secretary of state when it was a little infant. Now it’s in over 30 countries. And you’re gonna stop them? I don’t think so,” he said.

The presidential debate, six weeks before Election Day, was the first of three in the final stretch of the campaign. The general election foes’ first face-off came as polling consistently shows a tightening race, in national surveys as well as in the battlegrounds that will decide the election.

This put even more pressure on the candidates to turn in a stellar performance Monday night, and seize the advantage going into October. Polls show both candidates are viewed negatively by sizeable swaths of the electorate – but Clinton faced the primary task of settling questions about her honesty while Trump faced the task of proving to voters he’s ready for the nation’s highest office.

The debate, though, seemed to gloss over two of the biggest trouble spots in Clinton’s record – her personal email use as secretary of state and ethical questions surrounding the Clinton Foundation. The latter issue did not come up during the debate, while the emails were addressed briefly.

While Trump has assailed Clinton throughout the campaign as dishonest, the Clinton campaign increasingly has pushed a narrative that Trump is temperamentally unfit to lead. The former secretary of state has enjoyed some help from influential voices in the media establishment, with The New York Times and Washington Post both publishing editorials Monday morning echoing that theme.

But Trump has dismissed such critiques, maintaining the public confidence heading into Hofstra that he exuded throughout the Republican primaries – during which the first-time candidate and debater vanquished 16 foes and dominated the stage over the roughly dozen early-season debates.

That record rendered him a rival not to be underestimated by the Clinton camp, which spent days preparing the Democratic nominee in study and mock-debate sessions even while Trump was out campaigning last week.