Sen. Scott Brown is demanding Elizabeth Warren reimburse Massachusetts $276,000 to cover the cost of mailing voter registration forms to more than 500,000 welfare recipients, a move Brown alleges is designed to help Warren’s campaign.

“It’s been disturbing for a lot of people to learn that the state’s welfare department undertook an unprecedented voter registration drive at the behest of Elizabeth Warren’s daughter and the organization she represents,” Brown said in a statement Friday. “It is clear that this was done to aid Elizabeth Warren’s Senate campaign.”

But work on the lawsuit that led to the mailings began in early 2011, months before the Democrat even entered the race against Brown, according to an attorney working on the case.