The ad was announced the same day Brown and his top Democratic rival, Elizabeth WarrenElizabeth Ann WarrenDem senators demand Trump explain ties to Koch brothers 'Fearless Girl' statue to be moved away from Wall Street bull Sanders, Warren, O’Rourke inspire patriotic small donor waves MORE, signed a groundbreaking agreement to discourage outside groups and super-PACs from spending millions of dollars on ads in the race.

Warren launched her first ad in November, pushing back on negative ads aired against her by conservative group Crossroads GPS.

Listen to the ad: