Sen. Elizabeth WarrenElizabeth Ann WarrenSenate Dems protest vote on controversial court pick Dems call for hearings on Trump’s CFPB nominee to be put on hold Dems to propose legislation to prevent ICE from shackling pregnant women MORE (D-Mass.) endorsed a Democrat vying to represent her state’s sixth congressional district — for the second time this election cycle.

The rising Democratic star on Saturday offered her endorsement of 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, the Marine veteran Democrat who will face off against Republican businessman Richard Tisei in November.

That wouldn’t be unusual, except Warren had already endorsed a Democrat in the race: incumbent Rep. John Tierney (D-Mass.). Moulton surprised the nine-term lawmaker in the Democratic primary earlier this month, buoyed by high-profile endorsements including that of retired Army Gen. Stanley McChrystal, the former top U.S. commander in Afghanistan.

At a campaign event at a Massachusetts restaurant, Warren sang the praises of her party’s new nominee.

"I didn't win an election by myself. We did this together. We magnify our voices and make each other stronger in fighting for the values that we share,” Warren said. “I endorse a man who fights for our values every single day -- Seth Moulton all the way!"

The endorsement should help bolster Moulton’s lead in the race. A WBUR poll released Friday shows the Democrat with a 47-39 percent advantage in the race. Both candidates had identical favorability numbers - 42 percent - but Moulton appears to have the advantage in the lean Democratic district.