U.S. Rep. Joe Sestak, the Democratic candidate for Senate, is launching his first TV commercial of the fall campaign Tuesday, a populist spot that slams his Republican opponent as a corporate champion indifferent to the middle-class.

Former U.S. Rep. Pat Toomey "thinks corporations shouldn't pay any taxes," the ad says, using a clip from a 2007 CNBC telecast in which he advocated eliminating corporate taxes to help U.S. firms compete internationally and thus create more jobs.

Next, a series of mostly black-and-white photos of worried-looking families appears, as an announcer says, "The middle class is struggling." Then Toomey is shown speaking at a podium, with images of the New York Stock Exchange and the Wall Street sign in the background.

"Pat Toomey. He's for them . . . not for us," the ad concludes.

The move comes after weeks of attack ads by Toomey and advocacy groups supporting the Republican.

Two weeks ago, the Democratic Senatorial Campaign Committee began running ads that zeroed in on Toomey's former career as a Wall Street trader in derivatives, as well as his past advocacy of loosening regulation of the financial industry.

Toomey enjoys an average lead of 45 percent to 38 percent in polls, according to Pollster.com, a website that aggregates results of all independent polls in the race.

Sestak's campaign has booked at least $110,870 worth of time on broadcast and cable television in Harrisburg, Pittsburgh, Johnstown, and Wilkes-Barre, according to sources who track media buys. The campaign has reserved time through Sept. 6. For now, no ads are scheduled for the Philadelphia area.

Most of the money will be spent on broadcast television; the cable purchases are mostly for spots during Phillies games and Saturday's Penn State football opener.

Contact staff writer Thomas Fitzgerald at 215-854-2718 or tfitzgerald@phillynews.com.