U.S. Rep. Rush Holt on Thursday released a new Internet ad in his bid for a U.S. Senate seat.

Titled "Wall Street," the ad comes in two forms: a 15-second spot and a minute-long version. In it, Holt proposes to rein in stock speculation on Wall Street with a new "speculation tax" – a fraction of a penny on every transaction.

"These days, most stock trades aren't made by human beings," Holt says. "They're made by supercomputers that flip stocks at a fraction of a second, helping bankers get rich quick."

Long-term investors, Holt says, will not feel any effect from the tax, but speculators using supercomputers to analyze stocks and trade at lightning speed will generate millions that could be used for other purposes.

Holt, standing in front of a white board in a laboratory classroom-like set, says most Democrats don't have the nerve to support such a move. But he does.

"The computers on Wall Street are beating the rest of us up," Holt says. "So I say, let's fight back." Holt is vying for the Democratic nomination to run for the U.S. Senate seat left by the late Sen. Frank Lautenberg. He is running against Newark Mayor Cory Booker, U.S. Rep. Frank Pallone and state Assembly Speaker Sheila Oliver in the Democratic primary election, to be held Aug. 13.