Harris-Trump showdown: Where they stand on this top issue for voters

With a massive migrant crisis at the southern border, which exploded under the Biden administration, Trump again made the issue one of his top focuses on the 2024 campaign trail.

He has promised to finish the wall, over 450 miles of which were built during his administration. He has also promised to launch the "largest domestic deportation operation in American history" to deport millions of illegal immigrants.

On the issue of migrant crime, he has said he will invoke the Alien Enemies Act to remove gang members, drug dealers and others to end the "scourge of illegal alien gang violence once and for all." 

Meanwhile, he has looked to go beyond illegal immigration and also shut down migrant parole policies that have been used by the Biden administration to bring in hundreds of thousands of migrants via humanitarian parole.

"They use a little technicality so we don't call 'em, but that to me, that's illegal," he said Monday of the parole processes for Cuba, Haiti, Nicaragua and Venezuela.

It would likely involve the limiting of the CBP One app, which was expanded by the Biden administration to allow migrants to make appointments on the app at ports of entry.

A Trump administration would also likely seek to restore the 2019 Remain-in-Mexico policy and bring back down the number of refugee admissions. On Monday, he announced an additional policy, promising to slap a 25% tariff on incoming goods from Mexico.

"I'm going to inform [the Mexican president] on day one or sooner that if they don't stop this onslaught of criminals and drugs coming into our country, I'm going to immediately impose a 25% tariff on everything they send into the United States of America," he said.

She has also been dogged by her past of more radical stances when serving as a California senator and 2020 presidential candidate, including a promise to end government contracts with private prisons and decriminalize illegal crossings. A Harris campaign adviser told Fox that her positions have been "shaped by three years of effective governance as part of the Biden-Harris administration."

But as she has sought to present herself as the candidate best suited to handle the border crisis, she has emphasized her past as a prosecutor going after transnational criminal organizations.

"As Attorney General of California, Vice President Harris went after international drug gangs, human traffickers and cartels that smuggled guns, drugs, and human beings across the U.S.-Mexico border.

She has also repeatedly hammered Trump over his alleged role in torpedoing a bipartisan border security bill that was introduced in the Senate in January, accusing him of having "killed the border deal for his political gain."

It also included an emergency authority to allow officials to shut down entries at the southern border when they reach a certain level - but conservatives say it would solidify high levels of illegal immigration.

The bill would also expedite work permits for migrants released into the interior and tighten language for credible fear screenings into the U.S.

She has reiterated that she still wishes to see a pathway to citizenship for illegal immigrants passed if she is elected to the White House.

"We need a comprehensive plan," Harris said in September. "That includes what we need to do to fortify not only our border but deal with the fact that we also need to create pathways for people to earn citizenship."