A primary challenger would weaken Trump in general election, says polling editor

President TrumpDonald John TrumpRosenstein expected to leave DOJ next month: reports Allies wary of Shanahan's assurances with looming presence of Trump States file lawsuit seeking to block Trump's national emergency declaration MORE will be weakened in the 2020 general election if he first has to face a challenger during the GOP primary, according to RealClearPolitics Washington bureau chief Carl Cannon.

"These guys, if they get challenged, they soften up the president," Cannon told Hill.TV's Joe Concha in an interview that aired Tuesday on "What America's Thinking."

"To this day, Jimmy Carter blames Teddy Kennedy for losing to [former President] Reagan in that 1980 challenge," he added.

Cannon pointed out that a primary challenge means a president's campaign team needs to fundraise and spend money that would otherwise be designated for the general election.

"These campaigns are tough. You say negative things about the person, so independent voters remember them," Cannon said.

"When George H.W. Bush was running, Pat Buchanan gave him a scare in New Hampshire, but he brought up that taxes issue," Cannon added. "To this day, conservative Republicans will tell you, 'Oh, yeah, he lost on the taxes.' Well, the exit polls didn't show that, but Buchanan softened him up, and [former President] Clinton beat him."

A handful of Republicans, including outgoing Ohio Gov. John Kasich and Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeTrump suggests Heller lost reelection bid because he was 'hostile' during 2016 presidential campaign Live coverage: Trump delivers State of the Union Sasse’s jabs at Trump spark talk of primary challenger MORE (Ariz.), have been floated as potential primary challengers to Trump.

"You don't want to get challenged by your own party," Cannon said. "It is a problem. It is not something you just brush away."

— Julia Manchester