A super PAC with ties to Senate Majority leader Harry Reid has begun airing a television ad defending Senate hopeful Bruce Braley, who's been under siege for remarks he made about the prospect of Sen. Chuck Grassley chairing the Senate Judiciary Committee.

The Senate Majority PAC began airing a 30-second spot Monday across the state. In the ad, two farmers vouch for Braley, a four-term congressman who landed in hot water recently after a video surfaced in which he warned at a Texas fundraiser that Grassley, "a farmer from Iowa who never went to law school," might head the Judiciary Committee.

Braley apologized for the comments, but Republicans and conservative allies have been hammering him, saying he denigrated farmers and Grassley. A conservative group also launched a flight of TV ads highlighting the comment.

Braley hasn't responded himself with any paid media. But the super PAC's ad appears to be aimed at countering the criticism.

The ad features two men who say "farmers like us know him." They tell of Braley growing up in Iowa working in construction and detasseling, and how he's backed the farm bill and the Renewable Fuel Standard while in Congress.

"We don't pay attention to what people say. We look at what they do," one says. "People can say what they like. But we know Bruce."

The super PAC, which has run an ad praising Braley in the state, is spending more than $210,000 on the ad, according to a spokesman, who said in an email that it will run for 10 days.

The Senate Majority PAC is run by former aides to Reid. Last year, it got a $2.5 million contribution from former New York City Mayor Michael Bloomberg, according to the Sunlight Foundation.

The Republicans' campaign arm in the Senate also pointed to a $100,000 donation from the trial lawyers' PAC.

In a report Tuesday, the Sunlight Foundation said the Senate Majority PAC has spent $7.8 million so far this election cycle, more than any other outside group, with much of the spending going to ads criticizing Republican candidates.