Speaker Kevin McCarthy (R-Calif.) took aim at Homeland Security Secretary Alejandro Mayorkas during a visit to the U.S.-Mexico border on Thursday, fueling an argument that could help lay the groundwork for a potential impeachment.

“This has got to stop. And it starts with the Secretary of Homeland. Stop lying to the American public. Tell them the truth what’s happening, and change back the regulation that we had before so our border can be secure,” McCarthy said in a press conference from Cochise County, Ariz., with the border fence in the background.

McCarthy did not specify what he thought Mayorkas lied about, but Republicans have repeatedly dinged him for testifying in a congressional hearing last year that the border is secure.

The issue of whether there is “operational control” at the border is central to the argument from hard-line conservative House Republicans that Mayorkas should be impeached.

That term refers to the Secure Fence Act of 2006, a law that says operational control of the border means prevention “of all unlawful entries” to the United States.

McCarthy has not endorsed impeaching Mayorkas, but in November called on him to resign, saying that House GOP investigations will determine whether they can open an impeachment inquiry.

“What has changed from President Trump to President Biden? There has been no legislation change, but why has the border — why has this region gone from 66,000 people come across to 250,000?” McCarthy said.

The press conference took place on the private property of a rancher.

“His family has found 14 dead bodies on his ranch in just the last couple years,” McCarthy said. “Those are human bodies. He tells the story of his grandson smelling the body. That is different from a dead cow.”

“Why is that happening? Because the administration’s policies that is allowing it to happen,” McCarthy said. “When you look at the gaps in the wall. Why are they there? Why are these lights wired but not working? Because we got a new president that said to stop it. We paid for the metal to go up but it’s stored far away. There’s gaps that allow it to come in. That’s wrong.”

The trip marks McCarthy’s first visit to the border as Speaker. He was accompanied by four freshman House Republicans who flipped Democratic-held seats in 2022: Rep. Juan Ciscomani (Ariz.), whose district includes parts of Cochise County; Lori Chavez-DeRemer (Ore.), Jen Kiggans (Va.), and Derrick Van Orden (Wis.).

“There are two people that can really have an immediate impact on the situation in this country, and that’s President Biden and Secretary Mayorkas,” Ciscomani said. “They both have failed, and they have shown no interest in fixing this issue. So I invite him here to the border to see what we saw today. Talk to the people that we talked to today and realize what impact this is having in our communities.”

Ciscomani said that the purpose of the trip was not to discuss immigration reform, but to discuss border security.

“These are two different issues and we need to deal with them separately,” Ciscomani said.