Sen. Jeff Flake, a frequent critic of President Trump, said the New Yorker's rhetoric and governing style may invite a Republican primary opponent in 2020.
Flake (R-Ariz.) did not rule out running against Trump himself, in an interview with ABC's Jon Karl.
"I do wonder and I do worry that in the future, we'll be faced with President Trump running for reelection on one side, drilling down hard on a diminishing base, and on the other side you might have [a far-left candidate] like Bernie Sanders or Elizabeth Warren.
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 9, 2017
Flake said such a phenomenon would leave a "huge swath" of voters "in the middle" without a defined candidate.
"Go for it dude," Jones told Lea Gabrielle. "You can't even win a primary in your own state. That's why you're not running for reelection right now."
Flake is retiring in 2018.
"This is a guy who votes for Democrats and sends money to Democrats," Jones said of Flake, who published evidence of a check he sent to Sen.-Elect Doug Jones (D-Ala.) in protest of conservative Judge Roy Moore.
Country over Party pic.twitter.com/JZMTaEYdxQ
— Jeff Flake (@JeffFlake) December 5, 2017
Jim Kessler, a former aide to Sen. Charles Schumer (D-N.Y.), said Trump's approval rating "could freeze water" and that Republicans should be concerned about 2018 and 2020.
He said Virginia Gov-Elect Ralph Northam (D-Norfolk) was the moderate primary candidate against liberal former Rep. Tom Perriello (D-Ivy).
Kessler said Democrats are already starting to shift to the middle in elections to combat the more conservative Trump.
"If you give [Trump] a primary challenger, he's going to be fired up," Jones warned, saying the president can galvanize support with raucous rallies.
Watch more above.