Elizabeth Warren

Elizabeth Warren gestures during a forum at Stonehill College in Easton, Mass., on Tuesday. (Gary Higgins / Quincy Patriot Ledger / Associated Press)

Elizabeth Warren, the consumer advocate-turned-Massachusetts Senate candidate, is fighting back after a new ad from an independent group founded by Karl Rove accuses her of being too close to big business.

Warren has emerged as an early target of Rove's Crossroads GPS, which plans to be active in the 2012 races for House and Senate, as it was in the 2010 midterm elections. Warren is the likely Democratic candidate to face incumbent Republican Sen. Scott Brown, who won the seat once held by Edward M. Kennedy in a 2010 special election.

An early Crossroads ad claims Warren "sides with extreme left protests" in the Occupy Wall Street movement, which supports "radical redistribution of wealth." Now, the group charges that Warren oversaw a TARP program that "bail[ed] out the same banks that caused the financial meltdown."

Warren released a Web advertisement Friday calling the charge "ridiculous."

"I've spent years standing up to Wall Street and big banks," she said. "No attack ad, and certainly not one from Karl Rove and Wall Street, will change that."

The Massachusetts race could be one of the marquee contests in the battle for control of the Senate, now held narrowly by Democrats. It represents one of the few opportunities for Democrats to pick up a Republican-held seat; the party is defending 23 of its own.

A new poll this week conducted by the University of Massachusetts for the Boston Herald showed Warren leading Brown 49% to 42%. Brown had led Warren 41% to 38% in the university's September survey.