Both Democratic candidates Hillary Clinton and Bernie Sanders spoke passionately about the desire to stop deporting immigrants who entered the country illegally and to provide a path to citizenship at The Washington Post/Univision debate in Miami. (Sarah Parnass/The Washington Post)

Bernie Sanders and Hillary Clinton accused each other of either failing immigrants or pandering to them during a spirited debate Wednesday evening defined in part by the candidates’ most direct attacks on one another and on Republican front-runner Donald Trump.

Sanders, a senator from Vermont, said Clinton, the former secretary of state, had turned her back callously on children fleeing violence in Honduras, while he had wanted to welcome them into the United States two years ago.

“Secretary Clinton said, ‘Send them back,’ ” Sanders thundered near the start of the night.

“Misrepresentations can’t go unanswered here,” Clinton replied curtly, and she went on to say Sanders had supported the work of American “vigilantes” patrolling the southern border to stop illegal immigration. Sanders denied the charge.

The angry exchange set the tone for a two-hour debate that ranged over national and international issues and also explored the raw emotions surrounding the separation of immigrant families as the result of deportations. In front of an expressive audience at Miami Dade College, each candidate pledged to go further than President Obama to protect immigrants in the United States without proper documentation and to give them a path to achieve U.S. citizenship.

Washington Post-Univision Poll: Florida primary voters

The debate, sponsored by The Washington Post and the Spanish-language network Univision, was conducted partly in Spanish, and it was unusual for the emotional notes struck by audience members who recounted personal stories of immigration difficulties and who challenged the candidates for remedies.

The session came a day after Sanders won an upset victory in Michigan by attacking Clinton as a free-trader with little regard for American jobs. In that contest he also made surprising inroads with African Americans, among Clinton’s most reliable constituencies to date.

The next big test for both candidates will come Tuesday, when Democrats — and Republicans — vote in Florida, Illinois, Missouri, North Carolina and Ohio.

The biggest prize is Florida, the site of Wednesday’s debate. The most recent polls have shown Clinton with a sizable lead over Sanders here, beating him by more than 25 points and posting strong support among Hispanics. The debate Wednesday was the last time the candidates were scheduled to be face to face before the Tuesday primaries.

Clinton sought to turn the page quickly here from her embarrassing and unexpected loss in Michigan, which appeared to slow some of her recent momentum toward the nomination.

“This is a marathon, and it’s a marathon that can only be carried out by the kind of inclusive campaign that I’m running,” Clinton said, a sidelong swipe at Sanders’s base of support among white voters.

“It was a very close race, and we’ve had some of those,” Clinton said. “I’ve won some, I’ve lost some.”

During a debate hosted by The Washington Post and Univision in Miami, Democratic presidential candidate Bernie Sanders said it was a "mistake" for the U.S. to "go around overthrowing small Latin American countries," even in the case of the Castro regime in Cuba. (The Washington Post)

She angrily dismissed a question about whether she would quit the race if she is indicted as the result of an FBI investigation into the personal email system she set up when she was secretary of state and whether she or her senior advisers mishandled classified information as a result.

“It’s not going to happen,” she sputtered. “I’m not even going to answer that question.”

When given the chance, neither candidate took the opportunity to call Trump, the billionaire real estate developer who has a commanding lead in the race for the Republican nomination, a “racist.”

Clinton said she was disturbed by many things that Trump has said and stood for, including his call for a ban on Muslims seeking to enter the United States. She called such positions “un-American.”

“I think what he has promoted is not at all in keeping with American values,” she said. She mocked Trump’s plan to build what she called a “very tall wall” along the U.S.-Mexico border.

Sanders also stopped short of using the term “racist,” but he called Trump’s promise to deport all of the approximately 12 million immigrants who are here illegally “vulgar.”

“I think that the American people are never going to elect a president who insults Mexicans, who insults Muslims, who insults women, who insults African Americans,” Sanders said.

Immigration is an issue of keen interest in Florida, and the debate included a personal appeal from a woman in the audience, who asked in Spanish what each candidate could do to reunite families such as hers who have been divided by U.S. immigration policy.

“Ma’am, I will do everything I can to unite your family,” Sanders said. “Your children deserve to be with their mother.”

Clinton praised her “incredible act of courage” for sharing her story and said: “It’s time to bring families together.”

Clinton aggressively went after Sanders for voting against a comprehensive immigration reform bill in 2007 that was sponsored by Sen. Edward M. Kennedy (D-Mass.).

“Imagine where we would be today if we had achieved comprehensive immigration reform nine years ago,” Clinton said.

Sanders said that he had opposed the bill because of provisions on guest workers that would have kept them in working conditions he called “akin to slavery.” He noted that he voted for a 2013 bill that he said fixed some of those problems.

“They were cheated, they were abused, they were humiliated,” Sanders said.

Clinton said she doubted such a bill would have been supported by Kennedy, then-Sen. Barack Obama and herself. She was a U.S. senator from New York at the time.

“That was one of the many excuses used not to vote for the 2007 bill,” Clinton said of Sanders’s explanation.

Sanders countered that Clinton had taken less friendly positions toward undocumented immigrants on the issuing of driver’s licenses and on protecting those fleeing violence in Honduras.

The Michigan victory injected unexpected drama into a Democratic race that had seemed all but settled before Tuesday. Clinton had seemed on the verge of locking up the nomination, and her advisers maintain that is still the case.

But with Michigan, the biggest and most diverse state he has won so far, Sanders has a firmer claim to legitimacy and momentum. In pre-election polls in Michigan, Clinton had a lead of more than 20 percentage points. But on primary night, Sanders won the state by 1.5 points.

The candidates were pressed about their respective places in a race in which Clinton holds a commanding lead in the delegate count, particularly once superdelegates are factored in. With the support of those elected officials and other party leaders, Clinton has now collected 1,221 delegates to 571 for Sanders.

Sanders emphasized his signature issue — Wall Street reform and the country’s unequal distribution of wealth — and tweaked Clinton over closed-door speeches she gave to Wall Street firms after leaving the State Department.

He pushed Clinton to release the transcripts of those paid speeches she gave in the run-up to her presidential bid, including one to Goldman Sachs for which she received $225,000.

“When you get paid $225,000, that means that speech must have been an extraordinarily wonderful speech,” Sanders said, playfully saying that’s why she should share it.

Asked whether he thinks she said different things behind closed doors, Sanders said: “That is exactly what releasing the transcripts will tell us.”

Clinton countered that she has “a public record and you can look it up,” suggesting she has been tough on the financial sector.

Sanders has pledged to continue his insurgent campaign through the Democratic convention in July. Sanders’s powerful liberal appeal and proven ability to energize young supporters potentially saps enthusiasm and money from Clinton while exposing her to continued attacks that may weaken her before she ever faces a Republican opponent.

Sanders’s online fundraising prowess has all but guaranteed that he can stay in the race for as long as wants. His campaign sought to parlay his unexpected success in Michigan into another big push for donations, asking supporters to help him raise $5 million by midnight Wednesday — a feat that it said “would stun the establishment.”

Clinton campaign manager Robby Mook told reporters earlier Wednesday that the Michigan victory does not change the mathematical advantage that Clinton holds over Sanders.

“We are confident we are nearing the point where our delegate lead will essentially be insurmountable,” Mook said.