Democratic presidential candidates Hillary Clinton and Bernie Sanders reunited in Brooklyn, N.Y. on April 14 for a contentious CNN debate ahead of the New York primary. Here are the most contentious moments from that debate. (Sarah Parnass/The Washington Post)

Former secretary of state Hillary Clinton had a new line to sum up the differences between herself and Sen. Bernie Sanders: “Describing the problem is a lot easier than trying to solve it.”

That line, which Clinton used at least twice in Thursday night’s Democratic presidential debate on CNN, was meant to crystallize something that Clinton has been talking about for weeks now – trying to cast herself as the realist in the Democratic race, and Sanders as an idealist whose sweeping ideas would fall flat.

Clinton returned to that theme again and again in the debate. She embraced the legacy of President Obama, describing how much Obama had accomplished despite Republican opposition, and criticized Sanders for saying Obama should have done more. She blasted Sanders for an interview with the New York Daily News, in which he struggled to explain the details of implementing his own plan to “break up” big banks.

“I absolutely agree with the diagnosis. The diagnoses that we’ve got to do much more to finish the work,” of expanding health-care coverage and having the government pay for tuition at public colleges, Clinton said. “When you make proposals, and you’re running for president, you should be held accountable for whether the numbers add up.” That was met with cheers.

Sanders, when pressed about the logistics of these proposals, returned – as he has before -- to moral first principles. “Public colleges and universities tuition-free? Damn right. That is exactly what we should be doing,” Sanders said.

This debate carried a heavy New York inflection – in its liberal, urban politics, and in its participants’ habit of interrupting each other, while shouting at the volume of a passing subway train.

In addition, both candidates used their ties to New York as a way of grounding themselves. In his closing statement, Sanders talked about growing up in Brooklyn, the son of an immigrant. In Clinton’s closing, she referred to her years as a New York senator – a rare moment when the longtime Washington insider could cast herself as a Washington outsider, sent to the capital from somewhere else. “I’m asking for our support again,” Clinton said. “To take what we did in New York, and to take those New York values to the White House.”

Later in the debate, Sanders said that, if he were elected president, he would ask President Obama to withdraw the nomination of Merrick Garland to the Supreme Court – because Sanders did not want Garland to be confirmed before he could take over.

“I think we need a Supreme Court justice who would make it crystal clear—and this nominee has not done this – that he or she would vote to overturn Citizens United, to make sure that American democracy is not undermined,” Sanders said. He was referring to the “Citizens United” decision, which allowed corporations and labor unions to spend unlimited funds on direct advocacy for or against candidates.

Clinton declined to answer the question. “I am going to support the president. When I am president, I am going to take stock of where we are and move from there,” Clinton said.

During an exchange on foreign policy, Sanders criticized the Israeli military’s conduct in a 2014 military campaign in Gaza, saying it had been an over-reaction to attacks by the Palestinian group Hamas.

The Washington Post's Dan Balz asks what Brooklyn means to the people on the campaign trail ahead of CNN's Democratic presidential debate on April 14. (Dan Balz/The Washington Post)

“Was that a disproportionate attack? The answer is, I think it was,” Sanders said during the debate in Brooklyn, describing a military campaign that came in response to rocket attacks aimed at Israel from Gaza. The United Nations estimated that more than 2,100 people were killed in the Palestinian territories, and said that more than half of those killed were civilians.

Sanders had suspended his Jewish outreach coordinator earlier Thursday, after the revelation that she had criticized Israel’s prime minister, Benjamin Netanyahu, who oversaw that 2014 conflict.

Clinton, in her response at the debate, offered a more pro-Israeli outlook, saying that Hamas had contributed to the casualties by using civilians as cover for its fighters. “Of course, there have to be precautions taken. But even the most independent analysts will say that the way that Hamas places its weapons….it is terrible,” Clinton said.

Earlier in the debate, Clinton struggled with questions about the U.S. intervention in Libya – an intervention she supported, but which ultimately created a power vacuum that has allowed militias and the Islamic State to thrive.

“We did try, without success, because of the Libyans’ obstructions to our efforts,” Clinton said. If she were elected president, Clinton said, she would continue trying to restore order and government.

Sanders cast the intervention – which Clinton supported within the White House – as an example of her poor judgment, and linked it to Clinton’s vote for the Iraq war.

“This is the same type of mentality that supported the war in Iraq,” Sanders said. “We didn’t think thoroughly about what happens the day after you get rid of these dictators.”

Throughout the debate Clinton tied herself closely to President Obama and accused Sanders of criticizing him, closely embracing the president she ran so hard against in 2008.

“I’m getting a little bit concerned here. Because I really believe that the president has done an incredible job against great odds,” Clinton said, during a back-and-forth about climate change. She said that Sanders had been unnecessarily critical of Obama for the landmark deal signed in Paris a few months ago, in which more than 190 countries agreed to tackle the problem.

“We’ve got to get beyond paper right now. We have got to lead the world in transforming our energy system. Not tomorrow, but yesterday,” Sanders said.

On this subject, their argument was not as much about climate change – a subject both have called a worldwide crisis – but rather about tactics, and their approach to politics. Sanders, as before, called for sweeping steps: a tax on carbon-dioxide emissions, an end to “fracking” to extract natural gas, and other measures that would sharply change the U.S. energy system. He criticized Clinton for incrementalism.

“Those little steps are not enough,” Sanders said.

But Clinton replied that Sanders’ ideas were not politically or logistically feasible – and that trying to implement them would waste time. Her references to Obama were another way of making this argument: Clinton stressed what Obama had done, in spite of fierce Republican opposition in Congress.

“I don’t take a back seat to your legislation that you’ve introduced, that you haven’t been able to get passed,” she said, in reference to a bill that Sanders had proposed to set up a carbon tax.

Earlier, Sanders said Clinton, had used a “racist term” when she spoke of criminal “super-predators” in the 1990s, during the push for higher jail sentences.

“It was a racist term, and everybody knew it was a racist term,” Sanders said.

Clinton apologized for the “unintended” consequences of that push for tougher sentences, which has been blamed for an increase in the incarceration of African Americans.

“I’m sorry for the consequences that are unintended, and have had a very unfortunate impact on people’s lives. I’ve seen the results,” Clinton said. “I want to focus the attention of our country, and to make the changes we need to make. I want white people to recognize that there is systemic racism. It’s also in employment, it’s in housing, but it is in the criminal justice system.”

In the run-up to the New York primary, both Democratic candidates have focused on issues important to black voters and urban Democrats. Earlier in the debate, Clinton had blasted Sanders – again – for being too friendly to gun manufacturers and the gun lobby, taking control of the debate in its second half-hour.

At one point, Sanders laughed at a mention of an attack line from Clinton, which is that Vermont is the largest per-capita source of guns used in crimes in New York. The actual number of guns traced to Vermont is relatively small, but the state’s small population makes the per-capita number high. Sanders seemed to be chuckling at the argument, but Clinton interjected.

“It’s not a laughing matter,” she said, dodging the question about whether the per-capita statistic had been fair. “I take it really serious. Because I have spent more time than I care remember being with people who have lost loved ones” to gun violence.

Sanders struggled, again, to explain how his views on guns had been shaped by the fact that he represented a state with a large percentage of gun owners and a low rate of gun crime.

“What we need to do is to do everything we can to make sure that guns do not fall into the hands of people who do not have them,” Sanders said at last.

The two candidates also had a sustained argument about the national minimum wage, which indicated how Sanders has changed the terms of their race. When Clinton advocated raising the wage by 67 percent, she was booed for not going far enough.

“We will set a national level of $12 [per hour] and then urge anybody who wants to go above it, to go above it,” Clinton said, defending herself from boos from supporters of Sanders, who has called for a $15-per-hour national wage. “I want to get something done, and I think setting the goal to get to 12 is the way to go.”

Sanders attacked her for not calling for a $15-per-hour wage, and the two argued so loudly that CNN moderator Wolf Blitzer had to intervene. “If you’re both screaming at each other, the viewers won’t be able to hear either of you,” Blitzer said.

The Vermont senator earlier pledged to release his full 2014 tax returns on Friday, which he said will make clear what he and his wife donated to charity, among other details.

Last year, Sanders released several pages of his tax returns, but not the specifics of his donations and other deductions.

“We have very boring tax returns. No big money from speeches. No major investments. Unfortunately, I remain one of the poorer members of the United States Senate,” Sanders said. The details that Sanders released last year showed that the majority of his family’s $200,000 income came from his own salary as a senator.

Blitzer asked Sanders if he would release prior years, but Sanders demurred for the moment.

“Jane does ‘em,” Sanders said, meaning his wife Jane. He said that his wife had been busy on the campaign trail. “We will get ‘em out very shortly.”

The debate turned sharply – and quickly – negative, as Clinton and Sanders attacked each other’s judgment in its first minutes.

“I do question her judgment. I question her judgment, which voted for the war in Iraq, the worst foreign-policy blunder in the history of this country,” Sanders said in response to the first question from Blitzer. It was a repeat of language Sanders had used on the campaign trail, repeated now to Clinton’s face. “I don’t believe that that is the kind of judgment we need, to be the kind of president we need.”

Clinton, in turn, repeated her own campaign-trail barb: that Sanders had showed himself unprepared for the job of president, by struggling to explain even his own policies.

“Talk about judgment, and talk about the kinds of problems he had answering questions about even his core issues, breaking up the banks…He could not explain how that was to be done,” Clinton said, referring to a difficult interview Sanders had done with the New York Daily News editorial board.

“I think you need to have the judgment on day one to be both president and commander in chief.”

In the past, both Clinton and Sanders had tried to cast their race as a friendly competition between allies – arguing about tactics, but agreeing that either of them would be better at the job than a Republican. That era seems to be over. The two later jabbed each other about Clinton’s speeches to Wall Street firms, with Sanders intimating that she had grown too cozy with those firms, and Clinton saying there was no proof of that. “It’s always important to get your facts straight,” Clinton said. She talked, as she had before, about scolding Wall Street banks before the financial crisis.

“Secretary Clinton called them out. Oh my goodness, they must have been really crushed by this. And was that before or after you received huge sums of money by speaking engagements,” Sanders said, mocking her.

In the early going, Clinton was clearly better at one thing: playing to the home-state audience. She mentioned New York in her opening statement, and then returned to the subject a few minutes later, as a sly reference to the rough-and-tumble reputation of the borough she was in. Clinton said, with a sly tone in her voice, that she loved being in Brooklyn.

The debate — the fifth one-on-one meeting between Sanders and Clinton -- comes at a bitter time in the Democratic race: Clinton has taken a commanding lead in the battle for convention delegates, but Sanders has won a string of state contests, and has begun criticizing the front-runner in ever-stronger terms.

Earlier Thursday evening, the Sanders campaign suspended its newly hired coordinator for Jewish outreach, after reports that she had criticized Israeli Prime Minister Benjamin Netanyahu on Facebook.

The suspension of Simone Zimmerman, hired just two days before, was first reported by the New York Times. The cause of the suspension was a report in the Washington Free Beacon, which had found postings in which Zimmerman called Netanyahu “arrogant, deceptive, cynical, manipulative,” and used a vulgarity to refer to him.

“She is suspended while we take a look at this internally,” said Symone Sanders, a campaign spokeswoman, told The Washington Post Thursday evening.

On Thursday, new polls highlighted the state of the race — in which Clinton has accumulated a commanding lead in delegates, while still failing to build the kind of enthusiasm that usually swells behind the front-runner.

In fact, as Sanders has railed against Clinton’s ties to Wall Street, and criticized her cautious, incremental approach to governing, she has become less popular, even while she wins.

A Gallup poll released Thursday showed that, while 66 percent of Democrats viewed her favorably, 30 percent did not. The gap between those two numbers, which Gallup calls Clinton’s “net favorability,” was smaller than it had been at any time since last July. When the race began, Clinton’s net favorability was 63 percent.

But the only race Clinton needs to win now is the one for Democratic delegates. In that race, she is leading, and poised to increase her lead in the New York primary: a new NBC/Wall Street Journal/Marist College poll showed her with a 17-point advantage over Sanders in the state.

In the days leading up to the debate, Sanders has been unusually critical of the front-runner, questioning whether she was truly qualified to be president. Sanders cited Clinton’s acceptance of Wall Street money, her past support of big trade deals, and her vote in favor of the Iraq War as evidence of her poor judgment. Sanders later backed off that comment, saying that “of course” Clinton was qualified.

On Thursday, the Vermont senator condemned remarks by a warm-up speaker at a huge Sanders rally in Manhattan the day before. Paul Song, the executive chairman of the progressive Courage Campaign, had labeled establishment Democrats in Congress as “corporate Democratic whores,” who ought to be defeated and replaced by “Berniecrats.”

“There’s no room for language like that in our political discourse,” Sanders wrote on Twitter.

Wagner reported from New York.