The Democratic Senatorial Campaign Committee is up with its first spot in Pennsylvania's Senate race attacking former Rep. Pat Toomey (R-Pa.) for his past as a derivatives trader.

The spot charges that Toomey "helped pioneer the use of derivatives" and accuses him of contributing to the financial crisis. 

Toomey faces Rep. Joe Sestak (D-Pa.) in November.

Toomey's campaign is pushing back hard against the ad, which includes some questionable claims. The ad charges that Toomey wrote the law to weaken oversight of Wall Street. 

The reference is to the Gramm-Leach-Bliley Act, which repealed certain financial regulations. Toomey didn't have his name on the legislation as a co-sponsor, but he did vote for the measure and wrote on his congressional website at the time that he helped "craft" the bill. 

The derivatives attack is also one that Sen. Arlen Specter (D-Pa.) previously employed against Toomey to much criticism.

Toomey was a derivatives trader in the 1980s, but according to the Associated Press, he was not involved in the credit default swaps that backed mortgage securities. 

The latest Rasmussen poll in the race has Toomey up 6 points. A Quinnipiac poll from June showed the race in a dead heat.   

-Updated at 4:45 p.m.