I believe that failed talk-radio host Al Franken is going after Senator Norm Coleman for voting the same way that Senator Barack Obama did on the last energy bill:

The candidates also agreed that the country must work toward energy independence, with Coleman citing wind-power tax credits and other initiatives he helped pass in Congress, and Franken and Barkley criticizing him for voting for a bill that included tax credits for oil companies.
Turning to Coleman, Franken said: “There was no reason to do that to get wind credits unless you had senators who took money from big oil companies.”
The candidates agreed that Congress needs to work to regain the trust of the American people. Coleman reminded the audience that he pulled his negative ads last week because he didn’t want to add to peoples’ discomfort.