U.S. Sen. Cory Gardner — who didn’t vote for Donald Trump in 2016 — is now endorsing the president’s re-election.



The about-face surprised Republicans and Democrats alike in Colorado, but based on a poll released Thursday, it may be a smart political calculation.



A new Magellan Strategies survey conducted after the government shutdown shows an unwavering devotion to Trump among registered Republicans in Colorado, with 90 percent approving of his job performance.



“Cory has no choice, with this (level of) loyalty and devotion to Trump in everything he’s doing,” said David Flaherty at Magellan, a Republican polling firm.



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Eight in 10 Republican voters supported Trump’s decision to shut down the government and his push for a wall on the border with Mexico, according to the poll, which has margin of error of a 3.9 percentage points. To win in 2020, many Republicans believe the party needs to stand firm with the president.



“This shows you the power, arguably, about Donald Trump,” Flaherty added. Among Republicans, “what he says is what they care about, and he’s delivering for them.”



Gardner aligns with Trump on a number of issues, but given his hesitancy to embrace the president in 2016, the endorsement is widely viewed as a move to prevent a serious intra-party challenge to his own re-election bid. Trump even returned the favor with a reciprocal tweet thanking Gardner, saying “we will all win in 2020 together!”



Gardner’s stance on Trump is big debate in GOP

It remains an open question as to whether the alliance will help Gardner with Republicans, particularly the president’s hardcore supporters.



The senator’s recent opposition to the government shutdown and perceived wavering on a border wall left some of the president’s supporters “ready to feed him to the wolves,” said Steve Barlock, a 2016 Trump campaign Colorado co-chairman.

MORE: Five factors that will determine whether Cory Gardner can win in 2020

The Magellan poll found Republican voters overwhelmingly preferred uncompromising conservative candidates rather than moderates willing to work across the political aisle.



Barlock considered Gardner’s endorsement “a necessary move by him just to survive,” particularly after some prominent House and Senate candidates who kept a distance from Trump lost in the 2018 election.



And he added a warning: “We are not going to waste our time supporting him just to watch him jump back and forth. We want him to support Trump all the way through 2020.”



Gardner’s relationship with Trump is a topic of much debate within the party.



At a forum Tuesday for candidates competing to lead the state Republican Party, the moderator asked three different questions about whether Gardner should face a primary challenge and whether he is a strong enough Trump supporter.



State Rep. Susan Beckman, a candidate for party chairwoman, acknowledged the frustration among party activists and offered meager praise. “He’s doing pretty well,” she told the crowd at the Republican Women of Weld forum in Fort Lupton.



“I think he has lessened his chances of getting a primary by standing up and supporting the president,” she added.



Sherrie Gibson, the state party’s current vice chairwoman and a candidate for the top post, argued against a primary challenge to Gardner.



“We don’t want a situation where our future nominee has to limp across the finish line and then (emerge) bloody and bludgeoned to stand in front of the Democrats. We don’t want that. That does not help us win,” she said at the forum.



A Gardner campaign spokesman explained the Trump endorsement by pointing to leading contenders on the Democratic side, suggesting they are too radical for Colorado.



“He has said he supports President Trump because he wants him to be successful for Colorado, and is concerned about the impact candidates like Bernie Sanders and Kamala Harris would have on our state with their support for socialism-style policies,” said Casey Contres, Gardner’s newly named campaign manager, referring to Democratic proposals on health care.



In 2016, Gardner pulled his support for then-candidate Trump after a tape showed him bragging about sexually assaulting women. He said he would write in the name of vice presidential candidate Mike Pence, essentially voiding his vote.



But in the president’s first two years in office, Gardner won support from Trump for a bill to protect the state’s legal cannabis industry and backed the president’s nominees for the U.S. Supreme Court. He also campaigned alongside Trump during the 2018 election as chairman of the National Republican Senate Committee.



MORE: Cory Gardner is in charge of keeping the Republican U.S. Senate majority. Here’s how the job could impact his future.

Mike McAlpine, a conservative activist in Colorado, called Gardner’s decision to endorse Trump “outstanding.” But he’s not sure it will ward off a Republican primary challenger.



“I am certain there will be at least multiple challengers for his primary race,” said McAlpine, a delegate to the 2016 Republican National Convention.



Democrats will make endorsement reverberate into November

Even if the endorsement helps Gardner with Republican voters, it may weaken his standing with unaffiliated and Democratic voters that he needs to win a second term.



Magellan Strategies conducted a poll in November that found that only 23 percent of unaffiliated voters — the largest bloc in Colorado — would vote for Trump in 2020.



“You want to win a primary? You embrace the president,” said Flaherty, the pollster. “But good luck selling to unaffiliateds in Colorado — that’s an extremely different challenge to overcome.”



A Democratic poll conducted amid the government shutdown in January put Gardner’s favorability at 39 percent compared to 43 percent who viewed him unfavorably, essentially a statistical tie with the survey’s 4.4 percent margin of error.



And within the Republican Party, Trump is viewed more favorably than Gardner, 85 percent compared to 59 percent, according to Colorado pollster Keating-OnSight. The difference reflects that one in five voters aren’t familiar with Gardner, while most know Trump.



“Embracing the hugely unpopular president is a difficult decision,” said Curtis Hubbard, a Democratic consultant at Onsight. But you’ve got to get to the general election to even win the general election.”



What may unite Republicans and independent-minded voters is the Democratic agenda in Washington and Denver. GOP strategists suggest Democrats are pushing too far and may alienate middle-of-the-road voters — giving Gardner an opening.



Another opportunity is the crowded and unsettled Democratic field. Four Democrats have announced bids to challenge Gardner, including two former state lawmakers, but other big names remain on the sidelines.



Regardless of which candidate wins, Democrats plan to tie Gardner to Trump and the endorsement only cemented the link.



“They’ll make sure it’s about Trump and not about Cory,” Hubbard said. “I’m of the mind that (Gardner’s) an extremely talented politician and he shouldn’t be underestimated. But that decision (to endorse Trump) to me was a head-scratcher.”



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