GOV. CHARLIE BAKER’S announcement that he won’t seek a third term – and Lt. Gov. Karyn Polito’s decision not to try to succeed him  – not only creates a void when it comes to what Baker calls his “brand of Republicanism,” it creates an opening in the state’s broad political middle. 

Baker managed to maintain his Republican label while becoming even more popular with registered Democrats in Massachusetts than members of his own party, which has moved steadily to the right during his tenure. His exit, with no high-profile fellow moderate Republican waiting in the wings, raises big questions about the future of the state GOP and has implications for a Democratic primary that will also feel the ripple effects of his decision. 

Four candidates have declared as candidates for governor so far: former Republican state representative Geoff Diehl, a hard-right conservative who used Baker’s announcement to remind voters that he’s been endorsed by former president Donald Trump, and three progressive Democrats – state Sen. Sonia Chang-Diaz, former state senator Ben Downing, and Harvard professor Danielle Allen. 

Attorney General Maura Healey has said she’ll make a decision soon about entering the Democratic contest, a candidacy that most observers think is much more likely now with Baker out of the race. 

Baker, who shunned Trump and his party’s rightward migration, is part of a run of moderate Republican governors, starting with his mentor Bill Weld in 1990, who have defied the state’s strong Democratic tilt to hold the governor’s office for all but eight of the last 31 years. They have often been seen as a healthy check on the Democratic-dominated Legislature, a form of divided government that voters seem comfortable with. 

But the state Republican Party has been riven by infighting in recent years, with Baker sharply at odds with state party chairman Jim Lyons, a Trump supporter who has been critical of the governor and has led the party to the right. 

While many political pundits thought Baker was perhaps the only Republican who could win a governor’s race next year, Lyons celebrated his decision to opt out. 

Massachusetts is “turning a new page,” Lyons said in a statement. “Our party remains committed to the America-First agenda advocated by President Donald J. Trump, and it’s clear to me that Charlie Baker was shaken by President Trump’s endorsement of another Republican candidate in Geoff Diehl.” 

Other Republicans, however, say rallying behind a more conservative candidate like Diehl is not a path to victory.

Veering to the far right “is just a losing strategy,” said Janet Leombruno, a Republican State Committee member from Framingham and former aide to Polito. “There’s no pathway to victory with that. Not in Massachusetts.”

Since Lyons took the reins, the GOP has lost seats in both House and Senate, where they now claim just three out of 40 seats. On Tuesday, the party lost a special election for a House seat on the North Shore that had been in Republican hands for decades.  

Leombruno said the state Republican Party has “completely imploded” under Lyons’s leadership. “With him at the helm, we’re only going to be continuing to self-destruct,” she said. “People are just going to jump ship left and right because he’s taking us off a cliff.”

Ralph Whitehead, a retired journalism professor at the University of Massachusetts Amherst, said Baker’s decision is a Pyrrhic victory for Lyons, who presides over an ever-shrinking party. “I think you could say Jim Lyons is a big fish in a birdbath,” said Whitehead.

For Democrats, Baker’s exit could create a big opportunity among moderate voters who would otherwise have supported the Republican incumbent’s reelection. 

Democrats outnumber Republicans in the state more than 3-to-1, but both parties’ shares of the electorate have been shrinking, with 32 percent of voters registered as Democrats and just 10 percent registered as Republicans. The largest share by far are unenrolled in any party – 57 percent – and those voters are free to cast ballots in either party’s primary. 

That could mean more unenrolled voters casting ballots in next September’s Democratic primary and more of them potentially supporting a Democratic nominee if Diehl is the Republican candidate.

“My guess is that in a general election Healey would be in a very good position to appeal to a portion of them,” said Whitehead. 

It was hard to not see the first effort at that in a statement Healey issued on Wednesday after news of Baker’s decision. She called him a “valued partner” who has sought to find “common ground” with others in a politically divisive period. “I have deep regard and respect for the way he has led, with a commitment to doing what is right on behalf of the people of the Commonwealth,” she said. 

Allen also had positive words for Baker as well as Polito, thanking them “for their dedication to our well-being” and adding that “we should all be grateful that they stepped forward to lead.” 

Downing and Chang-Diaz, meanwhile, were critical of the status quo and said it is time to move on from Baker’s tenure and address problems facing the state that have been ignored. 

Another name that emerged on Wednesday as a potential Democratic candidate – and that could make a play for more moderate voters – is Marty Walsh. The former Boston mayor joined President Biden’s cabinet as labor secretary only eight months ago, but is said to have made no secret of his continued political ambitions in Massachusetts. Democratic political consultant Mary Anne Marsh said on WCVB-TV Wednesday afternoon that Walsh has been telling people he wants to run for governor. Peter Kadzis of WGBH News, however, quoted a close Walsh confidant as saying he would support Healey if she ran. 

Shannon Jenkins, a professor of political science at the University of Massachusetts Dartmouth, said given Baker’s popularity, there is room for a centrist candidate in the race, maybe from the private sector. “I think there is a hunger for a more moderate candidate like Charlie Baker particularly among unenrolled voters,” Jenkins said.

She said Diehl has an “upper limit” on the electoral support that he can get as a Trump-aligned Republican. With the Republican state party apparatus politically aligned with Diehl, a moderate GOP candidate would have to build up their own organization, including quickly ramping up fundraising or having private money to spend.

“Could a moderate emerge in the Republican Party and win? Yes,” Jenkins said. “Is it likely? I’m not sure.”

Tom Mountain, a Newton State Committee member and former Republican Party vice chair who supported Trump and is also a strong Baker supporter, said he is disappointed in Wednesday’s news because Baker would have been “unbeatable.” 

“The only way we Republicans can win statewide election is by having the unenrolled vote,” he said. Mountain said he remains hopeful voters will choose a Republican governor even without Baker in the race, to maintain a balance of power with the Democratic-controlled Legislature.

But others don’t share that optimism. Ed Lyons, a centrist Republican activist who is not related to – or a fan of – the state party chairman, said bluntly, “It’s over. There is no more party now… Culturally, it was Baker or bust, and now it’s bust.”

Massachusetts residents who are neither progressive nor conservative need to start thinking about a “post-party future,” Lyons said. “I believe there’s this huge middle of Massachusetts politics, a huge network of people, all of us will be talking in the next month to say are we going to let the middle go?”

Baker struck a more philosophical note at an afternoon press briefing where he and Polito formally announced their decision. The governor was asked whether his exit could mean the disappearance of his moderate approach to governing in today’s increasingly polarized political climate.

“I look at that a little more optimistically, I guess,” Baker said. “People say all the time that we’re sort of a center-right administration, moderate, whatever term you like best. But if you look at where we land with respect to the people of Massachusetts, the vast majority of them are basically in the same place we are. One way or another, they, the people of Massachusetts, will have a lot to say about the kind of political discourse and the kind of political behavior that they will choose to support here in the Commonwealth, and that will drive almost by definition the people who are playing in that environment to respect and respond to them.”