BY JENNIFER LEVITZ
LOWELL, Mass.—A battle here between Republican Sen. Scott Brown and likely Democratic challenger Elizabeth Warren in next year’s election is already drawing millions in out-of-state money because it could decide the Senate’s balance of power.
The race pits two nationally known candidates who have been elevated to prominence by separate populist waves. Mr. Brown, propelled by tea-party activists, scored an upset win in a special election in early 2010, capturing the seat long held by Democrat Edward Kennedy. Ms. Warren, a Harvard Law School professor and prominent consumer-finance watchdog, has tapped into the anti-Wall Street sentiment that is illustrated by …