WASHINGTON -- Massachusetts Gov. Charlie Baker (R) said Wednesday that he won't vote for Donald Trump, even if he becomes his party's presidential nominee. 

"I’m not going to vote for him in November," Baker told reporters, according to the Boston Globe, noting that he also didn't vote for Trump in the state's Super Tuesday primaries. Trump still easily won Massachusetts, capturing nearly half of the vote. 

Baker is the latest in a growing list of Republican officials who say they won't back Trump in the general election, which could cause problems for a party looking to unify and defeat the Democrats. 

New Mexico Gov. Susana Martinez, chair of the Republican Governors Association, hasn't gone quite as far as Baker, but on Tuesday, she refused to say whether she would back Trump in November if he becomes the nominee. She clarified, however, that she won't be voting for the Democratic nominee either.

Sen. Ben Sasse (R-Neb.) and Rep. Scott Rigell (R-Va.) also recently came out in recent days and said there's no way they'll be backing Trump this cycle. Rep. Reid Ribble (R-Wis.) ruled out backing Trump late last year. 

And on Tuesday, the chief strategist for Republican Mitt Romney's 2012 presidential campaign said he believed Democrat Hillary Clinton would be a better president than Trump. 

"Personally, I think Hillary Clinton would be a better president than Donald Trump because I think that Donald Trump is a dangerous person and is someone who would embarrass America," Stevens said.

But Trump has, slowly, started to pick up a bit of establishment support. Most notably, New Jersey Gov. Chris Christie (R) came out and endorsed Trump, although it seemed like the move was largely designed to spite Sens. Marco Rubio (R-Fla.) and Ted Cruz (R-Texas). 

Baker was a Christie backer, and he said he was "surprised" by the New Jersey governor's endorsement. 

On Twitter, the hashtag #NeverTrump has started to gain attention, with a growing number of die-hard Republicans admitting that they just couldn't ever bring themselves to back the GOP front-runner. 

"These people are not quietly concerned about Trump," wrote Bloomberg View columnist Megan McArdle. "They are appalled, repulsed, afraid and dismayed that their party could have let this happen. They wrote in the strongest possible language, and many were adamant that they would not stay home on Election Day, but in fact would vote for Hillary Clinton in the general and perhaps leave the Republican Party for good.

Former GOP presidential candidate Newt Gingrich on Tuesday criticized Republicans who are already vowing not to back Trump, saying, "I believe when you're faced with a choice with Clinton corruption, appointing radical judges with a disastrous foreign policy, it's very hard for any serious Republican to not support the Republican nominee."