Sen. Scott Brown (R-Mass.) is out with his first television ad of the election cycle, titled "Independent," which doesn't mention that he is a Republican.

"Tonight, the independent majority has delivered a great victory," says Brown, speaking after winning the 2010 special election. "He's turned out to be unpredictably independent and beholden to no one," says Lesley Stahl in a clip from "60 Minutes."

The ad is part of Brown's effort to cast himself as an independent in a state where most voters don't list a party affiliation but vote mostly for Democrats.

He faces a stiff challenge from likely Democratic nominee Harvard Law Professor Elizabeth Warren, who has been on the defensive recently over questions about her Native American heritage. She listed herself as Native American in law school directories in the 1980s and 1990s, being 1/32 Cherokee. Brown has called on her to release her job applications. The Warren campaign calls it a distraction, and she and Harvard have denied that she gained any benefit from it.

The controversy, at least, hasn't registered much in the polls, with the race still tied, according to a Rasmussen poll released Tuesday.