(WASHINGTON) — As President Donald Trump considers a replacement for fired FBI Director James Comey, lawmakers are urging the president to steer clear of appointing any politicians.

The advice came Sunday amid more criticism over Trump’s dismissal of Comey during an FBI probe of Russia’s meddling with last year’s election and any ties to the Trump campaign. James Clapper, the former director of national intelligence, said the Founding Fathers created three co-equal branches of government with checks and balances, but with Trump as president, that was now “eroding.”

“I think, in many ways, our institutions are under assault, both externally — and that’s the big news here, is the Russian interference in our election system,” Clapper said “I think as well our institutions are under assault internally.”

When asked, “Internally, from the president?” Clapper responded, “Exactly.”

The White House had no immediate comment. No White House aide appeared on the Sunday news shows, leaving Nikki Haley, the U.S. ambassador to the United Nations, to defend Trump. “The president is the CEO of the country. He can hire and fire whoever he wants,” she said.

Lawmakers from both parties reprimanded Trump for his actions, which included shifting explanations from the White House for Comey’s dismissal and an ominous tweet by Trump that warned Comey against leaks to the press because Trump may have “tapes” of their conversations.

Republican Sen. Lindsey Graham, a member of the Judiciary Committee, said selecting an FBI agent to lead the agency would allow the nation to “reset.” He dismissed as less desirable at least two of the 14 candidates under consideration, ex-FBI agent and former Rep. Mike Rogers of Michigan and Sen. John Cornyn of Texas, the No. 2 Republican in the Senate.

“It’s now time to pick somebody who comes from within the ranks, or has such…