Massachusetts House nominee Seth MoultonSeth Wilbur MoultonThe Hill's Morning Report — Battle lines drawn: Kavanaugh’s confirmation fight gets under way Dem generation gap widens The Hill's Morning Report — Sponsored by Better Medicare Alliance — Expensive and brutal: Inside the Supreme Court fight ahead MORE (D) released a campaign ad Thursday opposing sending U.S. troops back to Iraq.

"Four tours in Iraq — a war he opposed but didn’t want another to go in his place," the ad says. "And he doesn't want to send troops back there now."

It was not clear whether Moulton meant sending U.S. troops to Iraq as advisers or specifically into combat — or if he opposes U.S. military action in Iraq overall.

Moulton beat Rep. John Tierney (D) earlier this month in the Democratic primary, boosted by key endorsements from military personal, including retired Gen. Stanley McChrystal, the former top U.S. commander in Afghanistan. 

Moulton is now running against Republican Richard Tisei in a district that leans Democratic, and is expected to have a better chance to hold onto the district than Tierney would have. 

"Seth Moulton shares the values of the people in the 6th district," said Carrie Rankin, Moulton's communications director, in a statement. "From protecting Social Security and Medicare, to fighting for women's rights and our nation's veterans, Seth will stand up to extremists and fight for our families in Congress."

Moulton joined the Marine Corps infantry in 2001 and led an infantry platoon in the 2003 Iraq invasion. He was in the first Marine company to enter Baghdad, according to his campaign site biography.

—This post was updated at 1:30 p.m.