"This is not a sick system, Mr. President, nor is it a rigged system. Let's not sow distrust in our democratic institutions," Flake tweeted.

This is not a sick system, Mr. President, nor is it a rigged system. Let's not sow distrust in our democratic institutions. — Jeff Flake (@JeffFlake) December 8, 2017

The GOP senator was responding to Trump's comments during a rally in Pensacola, Fla., earlier Friday night when Trump responded to chants of "lock her up" by citing the "rigged system."

"It's being proven we have a rigged system. Doesn't happen so easy," Trump said. "But this system — gonna be a lot of changes. This is a rigged system."

"This is a sick system from the inside. And there's no country like our country, but we have a lot of sickness in some of our institutions," he continued. "We're working very hard, we've got a lot of them straightened out, but we do have, we really do, we have a rigged system in this country and we have to change it." Flake, a frequent critic of Trump, sat next to the president during a meeting at the White House earlier this week with other Republican senators to discuss trade.

During the meeting, Trump made a plug for Alabama Senate GOP candidate Roy Moore, who has faced allegations of sexual misconduct from multiple women who say he pursued them when they were teenagers.