(NewsNation) — With less than 100 days until the presidential election, the Donald Trump and Kamala Harris campaigns are touching on critical issues, including ongoing debates about the nation’s southern border.

Republican vice presidential nominee JD Vance hit the campaign trail in Arizona this week as he and Trump try to paint the Biden-Harris administration as weak on immigration issues.

“Some things are difficult,” Vance told NewsNation’s Ali Bradley on Thursday. “Border enforcement is common sense. You just need to power Border Patrol to do what they need to do.”

Listing the flow of fentanyl as a top concern, Vance said he’s also spoken to border officials about reinstating a “Remain in Mexico” policy and being “aggressive” with deportations.

“We know the cartels, but also a lot of other fraudsters, use the asylum process to come into the country illegally,” he said.

The Supreme Court initially issued a ruling on June 30, 2022, declaring that DHS Secretary Alejandro Mayorkas had the discretion to end the Migration Protection Protocols (MPP), sometimes informally referenced as the “Remain in Mexico” policy.

Under the Migration Protection Protocols, people encountered at the southwest border without U.S. citizenship were required to await their removal proceedings in Mexico rather than the U.S.

More than 9,600 non-U.S. citizens were enrolled in the program between Dec. 6, 2021, and June 30, 2022, according to the DHS. Of those, 5,755 people were returned to Mexico following their initial enrollment, according to a July 2022 DHS report.

Harris, the presumptive Democratic nominee, isn’t shying away from border issues, either. Her campaign released a new ad criticizing Trump after he effectively sunk a bipartisan border bill earlier this year.

The commercial attempts to present a clear choice to voters.

“The one who will fix our broken immigration system and the one who’s trying to stop her,” the ad says.

Biden gave Harris the responsibility of manning everything immigration along the southern border in 2021, with her role, according to the White House at the time, to stem the arrival of “irregular migrants.”

As recently as the Republican National Convention, Republicans heavily criticized the Biden-Harris approach to the border, a hot-button issue this election cycle.

Under the Biden-Harris administration, migrant encounters with the Border Patrol at the U.S.-Mexico border hit record highs at the end of 2023.

The Border Patrol had close to 250,000 encounters with migrants crossing into the U.S. from Mexico in December 2023, surpassing the previous high of 224,000 encounters in May 2022, also under the Biden-Harris watch.

Harris announced in March that $5.2 billion in pledges from private companies had been made to prop up Central American communities in an effort to deter illegal entry to the U.S. under her guidance.