GOP Sen. Thom Tillis warned Sunday that pressure campaigns to push President-elect Donald Trump’s Cabinet nominees through Congress “run a lot of risks,” including the possibility of backfiring on its very purpose.

“If anything they could create a structural problem for future nominees if they overreach,” Tillis (R-N.C.) said on “Fox News Sunday.”

More than a handful of Trump’s picks for his Cabinet have faced sharp skepticism over their character or qualifications or both, including Defense secretary nominee Pete Hegseth, Director of National Intelligence nominee Tulsi Gabbard and Health and Human Services nominee Robert F. Kennedy Jr. His original choice for attorney general, Matt Gaetz, already had to bow out.

Republicans will have 53 seats in the next Senate, enough to guarantee confirmation for appointees as long as Republicans stick together. Because of that, pressure campaigns are being mounted by Republicans lawmakers and third party organizations alike to get the nominees confirmed.

“A lot of these are third parties that are making money from the fund-raising campaigns, to put some ads in there but double digit percentages are going into their pockets,” Tillis said. “Here’s what I would tell them: If they really support President Trump’s nominees they should stand down and let the nominees win on their own merits and I think most of them will.”

One such third party supporting the nominees is Heritage Action, a conservative think tank that released an advertisement Friday attempting to “ensure the Senate conducts a swift confirmation process,” according to their social media post.

The North Carolina senator questioned the intention of such advertisements, but emphasized that he believed they are not coming “directly out of Mar-a-Lago.”

“It’s coming out of groups, sometimes they have good behavior and other times they’re out there to make some change and get their name out there as an activist organization,” he said. “I think that’s not doing the president a very good service.”

He added that the nominees need to be prepared to answer tough or even “unfair” questions, referencing the 2018 Brett Kavanaugh hearing for his nomination to the U.S. Supreme Court.

“Nothing is sacred — family, past experiences, personal experiences, high school yearbooks. The nominees need to get ready and they need to answer these questions to the satisfaction of the Republican members minimally,” Tillis said.