Former Senator Jeff Flake, one of President Donald Trump’s most vocal critics during his first administration, reacted to Sen. Thom Tillis’ retirement plans on Sunday.

Tillis, who was one of the most vulnerable Republicans in the 2026 cycle, had faced threats from Trump to endorse a challenger after Tillis voted against the president’s “big, beautiful bill,” on Saturday night.

In an X post, Flake speculated that Tillis could have won re-election, but only if he took certain positions.

“He could win again, but only by taking positions he doesn’t believe in,” Flake, who served as U.S. ambassador to Turkey during the Biden administration, said.

TRUMP’S ‘BIG, BEAUTIFUL BILL’ FACES REPUBLICAN FAMILY FEUD AS SENATE REVEALS ITS FINAL TEXT

Former Senator Jeff Flake responded to Tillis’ retirement announcement with sympathy on Sunday. (Getty Images)

“It’s an honor to serve in the Senate — but not at any cost,” he added.

Tillis said on Sunday that he plans to retire at the end of his term in 2026. In a statement, the North Carolina Republican referenced “the greatest form of hypocrisy in American politics.”

“When people see independent thinking on the other side, they cheer,” Tillis said. “But when those very same people see independent thinking coming from their side, they scorn, ostracize, and even censure.”

“In Washington over the last few years, it’s become increasingly evident that leaders who are willing to embrace bipartisanship, compromise, and demonstrate independent thinking are becoming an endangered species,” he added.

Tillis added that the choice broke down to either spending time with his family or navigating “the political theater and partisan gridlock,” in Washington, D.C.

“It’s not a hard choice, and I will not be seeking re-election,” he said.

SENATE REPUBLICANS RAM TRUMP’S ‘BIG, BEAUTIFUL BILL’ THROUGH KEY TEST VOTE

Sen. Thom Tillis (R-NC) departs from a luncheon with Senate Republicans at the U.S. Capitol Building on June 1, 2023, in Washington, DC. (Anna Moneymaker/Getty Images)

Senator Bernie Sanders, I-Vt., also reacted to Tillis’ announcement with a criticism of Trump.

“I do not agree with N.C. Senator Thom Tillis on much. But he’s right on this,” Sanders’ post began.

He added, “Trump’s Republican Party does not allow for independent thought. The Republican Party today is a cult. Either you do as Trump wants, or you’re out. Pathetic.”

On Saturday evening, Trump blasted Tillis as a “grandstander” and expressed interest in interviewing potential primary challengers.

“Numerous people have come forward wanting to run in the Primary against ‘Senator Thom’ Tillis,” Trump said on Truth Social. 

President Donald Trump speaks with reporters after announcing a trade deal with United Kingdom in the Oval Office of the White House, Thursday, May 8, 2025, in Washington. (AP Photo/Evan Vucci)

CLICK HERE TO GET THE FOX NEWS APP 

“I will be meeting with them over the coming weeks, looking for someone who will properly represent the Great People of North Carolina and, so importantly, the United States of America. Thank you for your attention to this matter!” he added.

Fox News Digital’s Alex Miller contributed to this report.