Using the hashtag #MuslimBan, Moulton tweeted that it’s “fundamentally un-American, doesn’t improve the vetting process and is making America less safe.” He also said “there’s no way in hell” that Generanl James Mattis, Trump’s new defense secretary, supports that policy.

Moulton, a decorated Iraq War veteran from Marblehead, is putting himself on the front line of opposition to President Trump — and right in the middle of the battle over Trump’s controversial executive order to keep citizens of some Muslim-majority countries out of the United States.

US REPRESENTATIVE SETH MOULTON knows opportunity when he sees it — and he’s seizing it, as he should.


“What I’ve heard from behind the scenes,’’ Moulton said during a telephone interview on Monday, is that Mattis and others who were left out of Trump’s decision-making loop on the immigration order are asking one another, “What will make you resign? What’s your red line?”

Added Moulton, who has worked with Mattis, “I’m sure General Mattis is thinking about that. I think he went into this administration believing he was on the inside and would have more of a role in preventing us from doing something truly dangerous for our country.”

Moulton’s a different kind of Massachusetts Democrat. A Harvard graduate, he became a Marine after 9/11 and served four tours of duty in Iraq, even though he said he opposed the war.

He’s also edgier and less concerned about collegiality. He first won office by beating longtime Democratic incumbent John Tierney. As a freshman congressman, he challenged President Obama’s push to send more troops to Iraq “without a plan to secure the peace,” as Moulton put it. He also backed Representative Tim Ryan of Ohio in his unsuccessful effort to oust Nancy Pelosi as House minority leader. In the aftermath, Moulton got a leadership position as senior whip to Steny Hoyer, the Democratic whip, and a seat on the House Armed Services Committee. He will also serve as vice chairman of an effort to reach out to younger Democrats.


Rather than boycott Trump’s inauguration, Moulton attended it, out of respect, he said, for democracy. But he also pledged to “stand for our values and to fight like hell.”

He’s been doing just that, particularly after Trump acted to ban refugees from Syria from entering the United States and block citizens from seven Muslim-majority countries from entering this country for 90 days. And Moulton’s getting noticed for his actions.

Exhibit A: A Sunday tweet from Bill Kristol, a Republican and founder of the conservative magazine, The Weekly Standard, stating that it was Moulton — not Senate majority leader Mitch McConnell — “who spoke for me,” after Moulton blasted Trump’s executive order.

In response, Moulton tweeted a thank you in which he praised Kristol’s “courage” and said, “We need more people on both sides to stand up for our shared American values.”

“I’m not going to back down one bit in attacking Trump,” said Moulton. “I’m also reaching across the aisle to encourage Republicans to stand up for our country. . . . Regardless of who you supported, there’s a lot of unease.”

Moulton’s adding his voice to the fray just as Democrats are listening for a voice for the future. Bernie Sanders is old. Pelosi has been around a long time, and so has Chuck Schumer of New York, the new minority leader in the Senate. Back in Massachusetts, Senator Elizabeth Warren is caught between unhappy supporters on the left and detractors on the right, who don’t like her ultra-liberal positions or demeanor.


Would Moulton take on another incumbent?

“I’m not even thinking about politics right now,” said Moulton. “I’m thinking about our Constitution and our values. Those are more important than anything else right now.”

Right now, they are.

Joan Vennochi can be reached at vennochi@globe.com. Follow her on Twitter @Joan_Vennochi.