The former president, Diehl said, is “strong on Crime, Election Integrity, our now under siege Southern Border, loves our Military, and has a big focus on taking care of our Vets.”

Republican Geoff Diehl’s campaign to unseat Mass Gov. Charlie Baker in the 2022 GOP primary gained some major momentum in early October when the former state rep and US Senate candidate earned the backing of former President Donald Trump.

Trump began his endorsement by lambasting Baker for his handling of COVID-19 vaccines and energy costs, and said the governor’s environmental views are “fresh out of the (Rep. Alexandria Ocasio-Cortez) playbook.”

“Baker is bad on crime, disrespects our police, does nothing for our Veterans, has totally botched the Vaccination rollout, presided over the collapse of the MBTA, and has seen crime go to record levels,” the statement read. “He has totally abandoned the principles of the Republican Party, never cutting taxes and undermining our agenda.”

The former president, Diehl said, is “strong on Crime, Election Integrity, our now under siege Southern Border, loves our Military, and has a big focus on taking care of our Vets.”

Diehl is challenging Baker, a moderate compared to much of the GOP, from the conservative mainstream of the Republican Party. The day before Trump’s endorsement, Diehl falsely claimed that the 2020 election results were “rigged.”

“Sadly, it has become clear as the audit results from Arizona, Georgia, and Pennsylvania have come to light, that the 2020 election was rigged,” Diehl said in a statement opposing mail-in voting. “We cannot allow mail-in voting, which does not protect the chain of custody of the ballots, to continue.”

Diehl’s campaign has claimed mail-in voting was linked to “fraud and inaccuracies” in the 2020 election. He also supports a conservative ballot initiative to install a voter ID law in Massachusetts. 

It’s a reversal for Diehl, who said months earlier that the Republican Party needed to move on and “stop crying over spilled milk.”

“I don’t think it was a stolen election,” Diehl told GBH News in July. “At this point we need to move forward.”

Critics of voting restrictions say laws disenfranchise would-be voters, particularly among the poor and people of color, leading to low-turnout elections.

The endorsement is almost certain to give the challenger a boost in the Republican primary. A March 2020 poll by WBUR found that Trump had a +70 net favorability (82% favorable, 12% unfavorable) among Bay State Republicans, while just 50% approved of Baker. (This was before pandemic lockdowns heightened conservative opposition.)

But Massachusetts Republicans are a small political minority in a state that rejected Trump resoundingly twice. Joe Biden beat Trump in Mass by 33 points, sweeping every county by double digits in 2020.

Even with weakening support, Baker looks as close to unbeatable as a Republican can be in a liberal state. He won his race by a 2-to-1 ratio in 2018, when Democrats surged across much of the country.

Diehl, meanwhile, won just 35% of the general vote in his failed 2018 bid to oust Sen. Elizabeth Warren.

If Baker is the nominee again for his third and final term, then Dems may see little hope in reclaiming the corner office. But if Diehl knocks off Baker in the GOP primary, Democrats have their opening to take complete control of the Massachusetts government.

In the 2018 primaries, Diehl cruised past two more moderate candidates, picking up 55% of the vote in a three-way race. Baker had no issue winning his 2018 primary, though he lost nearly 100,000 votes to a fringe hard-right candidate with very little campaign infrastructure or name recognition.

Currently seeking the Democratic nomination are state Sen. Sonia Rosa Chang-Díaz, former state Sen. Benjamin Downing, Harvard political science professor Danielle Allen, and business owner Orlando Silva.

Baker has yet to say whether or not he will run. If he decides not to, or if Diehl’s challenge becomes even more credible, the Dem field will likely open up.