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)

Former secretary of state Hillary Clinton, just one day removed from a stinging upset loss in the Michigan primary, used Wednesday’s Democratic presidential debate to launch sharp attacks on her rival, Sen. Bernie Sanders, criticizing him as too far left at some points, but also seeking to cast him as an ally of far-right militiamen on the subject of immigration.

The debate was sponsored by Univision and The Washington Post, and conducted in both English and Spanish: the candidates spoke only English, but questioners and moderators often spoke Spanish before being translated.

For Clinton, the attacks on Sanders were a sign that she is not yet able to pivot toward a general-election matchup against Republicans. Instead, she is still trying to make a case against Sanders – and looking ahead only to Florida, where she and Sanders face a crucial primary next Tuesday. At one point, Clinton sought to link Sanders to the “Minutemen” movement that was popular a decade ago, in which private militias sought to catch and deter those crossing the U.S.-Mexico border.

“Senator Sanders . . . stood with the Minutemen vigilantes in their ridiculous, absurd efforts to, quote, “hunt down immigrants,’” Clinton said at one point. She was referring to an episode in Congress, in which Sanders supported a bill that was designed to prevent the U.S. government from coordinating with Mexican authorities to thwart illegal immigration. Sanders’s staff has said previously that the senator believed the amendment was, in effect, harmeless: It would ban something that didn’t happen anyway.

Washington Post-Univision Poll: Florida primary voters

“No, I do not support vigilantes, and that is a horrific statement, an unfair statement to make,” Sanders said.

But Clinton also returned to arguments she has made in the past about Sanders’s sweeping liberal policy ideas, arguing that they are unrealistic: too complicated, too expensive, and too hard to pass. “If it sounds too good to be true, it probably is,” Clinton said.

Sanders may also have hurt himself, at least in Florida, with comments that edged close to the state’s traditional political taboo: praising the Castro regime in Cuba. Moderators played a 30 year-old tape in which Sanders – then the socialist mayor of Burlington, Vt. – praised Castro’s regime and criticized past efforts to overthrow him. Sanders said that the Cuban regime was autocratic, but also praised its results in improving health care and education on the island. He got cheers. But when Clinton criticized Sanders for praising the communists in Cuba, the cheers were louder.

Clinton also criticized Sanders for being too negative about recent Democratic presidents.

“Sen. Sanders is always criticizing the two recent Democratic presidents, President Clinton and Persident Obama. And that’s fine. But I wish he would criticize – and join me in criticizing – President George W. Bush,” said Clinton, who is married to another former president, Bill Clinton. She meant that Sanders was wrong to seek to replace “Obamacare” – President Obama’s signature health-care law – with a “single-payer” health-care system.

Sanders scoffed at the idea that he had not been critical of Bush.

Tracking the race to the Democratic nomination

“I gather Secretary Clinton hasn’t listened to too many of my speeches,” Sanders said, noting that he frequently criticizes the decision to invade Iraq. But Sanders said he would not shy away from criticizing Bill Clinton, especially for his decisions to approve deregulatory laws affecting Wall Street: “Let’s remember that’s when Wall Street deregulation took place. … Good things happened, but some dangerous mistakes were made,” Sanders said.

Sanders defended his plan to offer free tuition at public colleges during Wednesday’s Democratic debate, saying he didn’t mind that his plan would offer free tuition even to those who could pay – like, for example, the children and grandchildren of Republican front-runner Donald Trump.

“Absolutely” Trump’s progeny should get free tuition at a state school, Sanders said. “I don’t think they will. But Donald Trump’s kids can go to public school free. . . . We are going to get to Donald Trump by raising the taxes on the top one percent, and millionaires and billionaires.” Indeed, Sanders’ plans to make public school tuition-free call for the tuition to be funded by new taxes on Wall Street trades.

Clinton responded with a sharp version of an argument she has made since the first debates, saying that Sanders’s plans to offer free tuition and universal government-run health insurance will be expensive, unwieldy and very unlikely to be passed by Congress.

“This is going to be much more expensive than anything Sen. Sanders is admitting to. This is going to increase the federal government dramatically,” Clinton said. She quoted her own father, a staunch Republican: “If it sounds too good to be true, it probably is.”

“Really?” Sanders said. He charged that Clinton was, in effect, giving up before joining the fight: “If the rest of the world can do it, we can,” Sanders said, meaning that many other industrialized countries offer universal health insurance.

Earlier, Clinton made an unusually personal admission of her political failings in Wednesday night’s Democratic debate, saying that politics “isn’t easy for me.”

“I am not a natural politician, in case you haven’t noticed, like my husband or President Obama, so I have a view that that I have to do the best I can,” Clinton said, in a response to a question from moderator Karen Tumulty about why so many voters consider Clinton untrustworthy, even after so many years in public life. “And hope that people see that I’m fighting for them.”

That admission, ironically, came after a powerful moment, in which Clinton came close to doing what her husband Bill Clinton was famous for: making an audience feel someone’s pain. A woman in the audience had described the difficulties she had faced after her husband, an undocumented immigrant, was deported.

Sanders had responded to her emotional question with a promise to help, by changing U.S. policy as president. “The essence of what we are trying to do is to unite families, not to divide families,” Sanders said.

Clinton began her response by focusing on the woman herself. “Please know how brave I think you are, coming here with your children to tell your story. This is an incredible act of courage that I’m not sure many people really understand. And I want you to know that,” Clinton said.

Later in Wednesday’s debate, moderator Jorge Ramos asked Clinton about the 2012 attacks in Benghazi, Libya, in which four Americans were killed – including the U.S. ambassador to Libya. Clinton was the secretary of state at the time, and Republicans have raised questions about whether Clinton had properly prepared State Department installations in Libya for attacks, and about whether she had misled the public about the cause of the attack.

When Ramos began to ask the question, the debate’s audience began to boo at the mention of the word “Benghazi.” He kept on, playing the tape of a relative of one of the four who died, who said she believed that Clinton had misled her about the attacks – saying they had been reactions to an anti-Islam video, rather than planned terrorist attacks.

“She’s wrong. She’s absolutely wrong,” Clinton said about the woman. She said that the explanation she had given to the families was based on what she believed at the time – which was later found to be incomplete and partially incorrect. “This was fog. This was complicated.”

Earlier in the debate, both candidates seemed to break with President Obama on the subject of immigration in Wednesday’s Democratic debate, with both saying that they would not deport children who were living in the U.S. illegally – a rejection of the Obama administration’s decision to deport children along with their families, if they have arrived recently and have been ordered deported by the judge.

“Stop the raids. Stop the roundups,” Clinton said, after close questioning by Univision moderator Jorge Ramos. “I will not deport children. I do not want to deport family members, either.”

Sanders agreed, saying that he agreed with Obama on many subjects, but “he is wrong on this issue of deportation.”

The Obama administration has been criticized for these deportation raids, which focus on immigrants who arrived recently from countries in Central America, were not granted asylum in the U.S., and then were ordered deported. American authorities have said they want to deter future waves of illegal immigrants, especially waves of children travelling alone.

Clinton and Sanders spent much of the debate’s early going arguing about past – largely failed – bills in Congress, and the positions they took on them. Clinton, in particular, criticized Sanders for supporting a 2007 amendment that was designed to help the “Minutemen,” a private group that patrolled the U.S. border in hopes of deterring immigration. According to a 2015 BuzzFeed story on that vote, Sanders has said that the measure was seen as largely a minor, empty gesture, and that it had strong support from Democrats at the time.

“No, I did not support vigilantes,” Sanders said, after Clinton had brought it up more than once. “And that is a horrific statement.”

Their first disagreement was about how significant it was that Sanders had defeated Clinton in Michigan the night before.

“One of the major political upsets in modern American history,” Sanders called it.

Clinton said, in essence, that it was a bump in the road.

“Well, look, I won one of the contests and lost another close one,” she said, referring to her lopsided win in Mississippi. “I was pleased that I got 100,000 more votes than my opponent, and also more delegates.”

At the outset of the debate, both candidates expressed support for immigration reform – a nod to their setting, and to the audience watching on Univision, which along with The Washington Post was sponsoring Wednesday’s debate. Sanders offered another nod to the location: a mention of climate change, a major cause of rising sea levels that threaten to encroach on Miami in coming years.

“We know that we have got to combat climate change,” Sanders said.

In the debate’s early going, moderator Jorge Ramos asked Clinton who had given her permission to use a private email server for government business.

“It was not prohibited. It was not in any way disallowed,” Clinton said. “There was no permission to be asked.”

Would Clinton drop out of the race, Ramos asked, if an FBI inquiry into her use of those emails ended with her being indicted?

“That is not going to happen. I’m not even answering that question,” Clinton said.

Both candidates criticized Republican front-runner Donald Trump, who has called for mass deportation of undocumented immigrants, and said many undocumented Mexican immigrants were rapists.

“I said ‘Basta!’” Clinton said, using the Spanish word for “enough.” She refused to say if she believes Trump is a racist, but criticized his rhetoric as damaging – especially to Trump’s prospects in a general election.

The debate can be streamed live at washingtonpost.com, or viewed on television: CNN is broadcasting it in English, and Univision is broadcasting in Spanish. The Washington Post and Univision are sponsors of this debate, which will be the fourth time that Clinton and Sanders have debated one-on-one.

Before Tuesday, Clinton seemed on the verge of locking up the nomination. But then Sanders won Michigan — the biggest and most diverse state he has won so far.

Clinton is still the clear leader in terms of states won and delegates accumulated. She added to her delegate lead Tuesday by winning a lopsided victory in Mississippi and dividing Michigan’s delegates nearly evenly with Sanders.

But after the Michigan win, it is clear that Sanders — the self-described “democratic socialist” running an insurgent campaign on Clinton’s left — has not peaked.

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

The biggest prize of them all is Florida, the site of Wednesday’s debate.

The most recent polls have shown Clinton with a sizeable lead over Sanders in the Sunshine State, beating him by more than 25 points. Wednesday’s debate will be one of Sanders’s last, best opportunities to turn that around.

John Wagner and Anne Gearan contributed to this report from Miami.