U.S. Rep. Michael Capuano yesterday joined a growing list of powerful Democrats who won’t commit to voting for one of their own in the 2018 gubernatorial race against presumed front-runner, Republican Gov. Charlie Baker.

“I can’t remember the last time, if ever, I voted for a Republican, you know. But it happens and guess what? I judge people on who they are,” Capuano, a Somerville Democrat, said on Boston Herald Radio.

When pressed on his opinion of Baker, Capuano said he’s known the governor for a “long time” and called him a “good man.”

“Overall, I think he’s doing a good job,” Capuano said of the Swampscott Republican. “And it’s always the job of the people challenging an incumbent not just to say what they would do, but also say what the failings are of the person they’re running against — that’s normal. So let’s have that discussion and that debate.”

Capuano’s comments hew close to those of House Speaker Robert A. DeLeo and Mayor Martin J. Walsh, both of whom have in recent months said that they want to see who the Democratic nominee is before committing to voting for him or her. Walsh, for one, said in a radio interview in April he’s “not ruling out anything” when it comes to his vote in 2018.

Capuano, however, also has a history of speaking warmly about Baker, even if, as he says, he didn’t vote for him in 2014. During the Democratic primary that year, Capuano indicated that eventual nominee Martha Coakley may not be the best candidate, while adding of Baker: “I think he’d be a good governor.”

Baker is widely expected to run for re-election. On the Democratic side, three candidates have emerged: Newton Mayor Setti Warren; Jay Gonzalez, a former Deval Patrick administration budget chief; and environmentalist Bob Massie.