When President Biden and former President Trump take the stage in Atlanta on Thursday, immigration and the humanitarian crisis at the southern border will almost certainly be a flashpoint.

Many polls show that voters believe Trump is best positioned to address the issue, and he has continuously slammed Biden on it. He has blamed his successor’s policies for the crisis, and filled his social media feeds with missives about crimes allegedly committed by immigrants, referring to them as “Biden Migrant Killings.” He has vowed to deport millions of immigrants who are in the country without legal authorization.

Trump has referred to migrants as “animals” and even suggested they should be turned into mixed martial arts combatants.

“I said, ‘Dana, I have an idea for you to make a lot of money. You’re going to go and start a new migrant fight league, only migrants,’” Trump said before an evangelical Christian conference in Washington, D.C., last weekend, referring to Dana White, head of the Ultimate Fighting Championship.

Such comments have scored Trump points with his base and beyond.

Biden faces a trickier challenge, allies and advisors say, and needs to hone in on a nuanced message Thursday night that emphasizes the balance between the need for border security and humanity for immigrants who already have entered this country.

“I don’t think it’s an either-or and I don’t think the American public thinks it’s an either-or,” Sen. Alex Padilla (D-Calif.) told The Times this week. “We can and should do both.”

He said Thursday night’s debate will exemplify how “Joe Biden speaks to American people. Donald Trump speaks to his base.”

Matt A. Barreto, a Biden campaign pollster, said an April poll he oversaw found that two-thirds of respondents in key battleground states want “a balanced approach to the immigration system and report high levels of support for policies addressing both border security and paths to citizenship.”

“This is what the president is pushing for and the polling data suggests that’s what the American public wants,” Barreto told The Times. “They want to see a well managed orderly border and they also have tremendous empathy for long-term undocumented immigrants and they want to see them brought out of the shadows.”

Biden has made two moves recently that reflect this balancing act, imposing limits on asylum seekers and clearing a path to citizenship for undocumented spouses of American citizens.

For the third month in a row, respondents to an April Gallup poll cited immigration as the most important problem facing the United States. A recent Washington Post-Schar School of Policy and Government poll of swing state voters found that just 42% of respondents said immigrants who are in the country illegally should be deported. Nearly 60% said they should be offered the chance to apply for legal status.

Still, Trump’s handling of immigration is preferred to Biden’s, 52% to 26%, according to the same poll.

During the debate, Trump is likely to bring up serious crimes allegedly committed by undocumented immigrants.

In one instance, two men from Venezuela who entered the U.S. illegally earlier this year were charged in connection with the death of a 12-year-old girl in Houston. “We have a new Biden Migrant Killing — It’s only going to get worse, and it’s all Crooked Joe Biden’s fault,” Trump said on Truth Social.

But immigrants are less likely to commit crimes than people born in the U.S., studies show. The Times reported earlier this year that Trump was fundraising with Thomas Homan, a former acting director of U.S. Immigration and Customs Enforcement who helped implement the widely derided family separation policy.

In response, Trump spokesperson Karoline Leavitt said, “Biden’s reversal of President Trump’s immigration policies has created an unprecedented and illegal immigration, humanitarian and national security crisis on our southern border.”

Leavitt said that if Trump returns to the Oval Office, “he will restore all of his prior policies, implement brand new crackdowns that will send shock waves to all the world’s criminal smugglers, and marshal every federal and state power necessary to institute the largest deportation operation in American history.”

In recent weeks Trump has appeared to modulate, saying on a podcast that immigrants who graduate from American colleges should get a green card. The comments prompted fierce pushback from his allies.

His spokesperson then clarified that not all graduates would be getting green cards, saying it “would only apply to the most thoroughly vetted college graduates who would never undercut American wages or workers.”

Earlier this year, House Republicans heeded Trump’s demands and killed a bipartisan border security bill after months of negotiations in the Senate. The negotiations also exposed divisions among Democrats and reflected the two notes Biden will need to hit Thursday: How to speak to voters who think the southern border is too porous while also emphasizing the contributions of immigrants already in the country.

“Every American should know that Trump proudly killed the strongest bipartisan border bill in a generation — siding with fentanyl traffickers over the Border Patrol and our security,” said campaign spokesperson Kevin Munoz, hinting at an avenue of attack Biden might utilize Thursday.

Padilla opposed the winter compromise because it didn’t include reforms to aid farmworkers and undocumented immigrants already in the country. Biden at the time said he would have signed the deal but it never made it to his desk primarily because of Trump’s opposition.

Even though he didn’t like the deal, Padilla said Biden has done a good job through executive orders and public pronouncements aimed at both securing the southern border and helping people already here. Padilla pointed to a recent executive order that would protect immigrant spouses of U.S. citizens who have lived consecutively in the country for at least a decade. The move allows as many as 500,000 of those immigrants to quickly access a pathway to U.S. citizenship.

Unlike Padilla, Rep. Greg Stanton (D-Ariz.) supported the Senate compromise deal. The former Phoenix mayor viewed it as a good start that immediately spoke to the frustrations of his constituents and would’ve “reestablished operational control” of the border. Stanton has frequently traveled to border stations and ports of entry — often with Republicans — and said that what he has witnessed is unsustainable.

Earlier this month, the Biden administration raised the legal standard for asylum claims and restricted access to asylum for those crossing the border illegally when arrests average higher than 2,500 a day, as has been common.

The change is hampered without additional funding, which the border bill would have provided, administration officials point out. Mexico has agreed to accept migrants from certain other countries, such as Venezuela and Cuba, allowing some to be quickly removed from the U.S. But officials can’t rely on the consistent cooperation of other countries, such as China, to take their citizens back.

Still, after record high arrests at the end of last year, Border Patrol said preliminary data since Biden’s announcement showed arrests had fallen by 25%.

May figures show arrests fell to the third-lowest of any month throughout his presidency.

Customs and Border Protection reported that agents recovered 895 remains of migrants in fiscal year 2022, three times as many as were discovered in 2018. Advocates say the number is a vast undercount.

Stanton said the debate is a moment where Biden can point to these accomplishments and lay out how Republican intransigency has torpedoed any efforts to get more durable fixes. Stanton was at the signing ceremony for Biden’s executive order where he highlighted the work of a formerly undocumented nurse who helped COVID-19 patients during the pandemic. The nurse had benefited from Deferred Action for Childhood Arrivals.

“Biden understands the fundamentals of saying you need strong border security and appropriate immigration, smart immigration reform,” Stanton said. “Those have always gone together.”

Times staff writer Andrea Castillo contributed to this report.