The president rarely wades into down-ballot politics, so it's indicative of just how important this race is for Democratic control of the Senate that he decided to weigh in on the race between Warren and Sen. Scott Brown (R-Mass.).
"Elizabeth Warren will be a strong, tireless and determined advocate for the people of Massachusetts, building on her remarkable record of working to help middle-class families get ahead," he said in a statement.
"Her life's work has been helping ordinary Americans get the fair shot they need and deserve. Elizabeth's passionate advocacy on behalf of consumers led to the Consumer Financial Protection Bureau. The agency is now protecting people from being taken advantage of by powerful companies. I know I can count on Elizabeth to stand with me to create jobs and opportunity for the people of Massachusetts and keep our country moving forward."
Warren has received a number of high-profile endorsements from the Massachusetts area, most notably that of Boston Mayor Thomas Menino, but Obama is her highest-profile yet — and it's hard to see how she'd be able to roll out any name bigger than his.
Obama's endorsement comes at a pivotal time in the Senate race. With just three weeks left until Election Day, the race remains within the margin of error, with Warren posting slight momentum in most recent polls. And Obama has held a double-digit lead over Mitt Romney in every poll of the Bay State since June, so his name and his backing could be enough to give Warren a boost into the lead.