A longtime nonpartisan political analyst predicted Monday that Colorado Sen. Cory Gardner’s endorsement of Trump has “shut the door” on any efforts to primary the first-term Republican prior to his expected re-election bid in 2020.

Sen. Gardner and Trump on Air Force One

In an appearance on Colorado Public Radio Monday, Jennifer Duffy, a senior editor at the Cook Political Report, had this to say about Gardner’s endorsement of Trump:

“I think [Gardner], one: endorsed the inevitable, but two: he also sent a message to Trump supporters in the state that he was with the president because – as a lot of Republicans learned in 2018 – to be against the president is to pretty much earn yourself a primary opponent,” said Duffy. “So he shut that door.”

Since Gardner took office, he has faced livid attacks from base Republicans, who see him as mealy-mouthed and have floated the name of State Rep. Patrick Neville (R-Castle Rock) as a great choice to challenge Gardner in a primary. Earlier this year, GOP gadflys, like Marc Zarlengo, and others, called for someone to challenge Gardner.

But Gardner’s endorsement of Trump could indeed help stave off a primary challenge, said Steve Barlock, who led the Trump campaign in Denver.

“Cory had only only one way to protect himself, and that was to endorse Trump,” said Barlock, adding that the “Trump base” in Colorado was completely infuriated at Gardner’s path-breaking decision to support ending the partial government shutdown without funding a border wall.

Gardner needs to support Trump “100 percent” going forward, said Barlock.

“It will be, ‘Cory, did you do everything for Trump? We’re voting for you. If you didn’t do everything for Trump, you’re on your own, buddy,'” said Barlock.

KNUS 710-AM radio host Julie Hayden says Gardner’s endorsement of Trump isn’t very meaningful to Republicans who don’t trust Gardner, but this doesn’t mean a primary is likely or would be successful.

“Cory Gardner’s endorsement of Trump does not do a heck of a lot right now to impress the Republicans who have had concerns about Gardner,” said Hayden. “From my point of view, Cory Gardner seems to flip flop and endorse Trump when he thinks it’s good for him. So I don’t think people like me are swayed by [Gardner endorsing Trump].”

In fact, Gardner, who called Trump a “buffoon in 2015,” said in March of 2016 that he’d vote for the mogul after he was asked seven times in a row by the Wall Street Journal whether he’d do so. A few months later, after Trump’s infamous pussy-grabbing comment come to light, Gardner said flatly, “I will not vote for Donald Trump.”

“I cannot and will not support someone who brags about degrading and assaulting women,” Gardner said at the time, promising to vote for Mike Pence instead. 

Gardner now has a 90 percent lifetime pro-Trump voting record, which has fallen to 50 percent pro-Trump during the current congressional session.

“People like me are going to be keeping a very close eye on what Cory Gardner says and does,” said Hayden, who’s a former reporter at Fox 31 Denver.

Hayden added that, while she likes other Republicans more than Gardner on the issues, the chances of anyone mounting a successful primary challenge against Gardner are extremely low, given his likely financial advantage.

Gardner followed his Trump endorsement last week with a rare visit to a Republican organizational meeting in Adams County, according to local GOP district captain Ben Nicholas, speaking to Hayden on KNUS Monday.

Gardner surprised Adams GOP attendees by “finally” appearing at the meeting, after six years of “avoiding us like the plague,” said Nicholas on air.

This could be another signal, in addition to his unexpected Trump endorsement, that Gardner is trying head off a conservative primary challenge before it starts frothing at the mouth in public.

Shortly after the November election, GOP pollster David Flaherty said Gardner could “very well” face a primary challenge, but it would have a “minuscule” chance of success.