Harvard Professor Elizabeth WarrenElizabeth Ann WarrenOvernight Finance: Lawmakers grill Equifax chief over hack | Wells Fargo CEO defends bank's progress | Trump jokes Puerto Rico threw budget 'out of whack' | Mortgage tax fight tests industry clout Michelle Obama is exactly who the Democrats need to win big in 2020 Wells Fargo chief defends bank's progress in tense Senate hearing MORE, who is likely to challenge Sen. Scott Brown (R-Mass.), on Thursday launched an exploratory committee and website.

Warren, a Democrat and consumer advocate who helped create the Consumer Financial Protection Bureau, has met with Democratic activists around Boston in recent days and is working with Doug Rubin, a senior strategist for Massachusetts Gov. Deval Patrick (D). She plans to announce her decision sometime after Labor Day.

She has been recruited heavily by Democrats, who believe Brown is beatable in the dark blue state but that none of the current crop of candidates, which includes City Year founder Alan Khazei, Newton Mayor Setti Warren and state Rep. Tom Conroy, are likely to make the race competitive.

Once it became clear Warren would not be appointed head of the CFPB because Republicans in the Senate would fight her confirmation, Democrats and liberals ramped up efforts to get her to run.

The liberal Progressive Change Campaign Committee has already raised $100,000 on her behalf in an effort to draft her into the race.

Brown will be tough to beat: His approval rating remains higher than 50 percent in recent polls, and he has almost $10 million in the bank for the race.