Senate Democrats are hoping to build momentum with grassroots activists around the issue of tax breaks for major oil companies.

Democrats have been pressing to repeal of billions of dollars' worth of industry tax breaks and apply the savings to deficit reduction. In conjunction with the party's effort in Washington, the Democratic Senatorial Campaign Committee (DSCC) has launched an online petition urging activists to support its stance.

Through Google and Facebook advertisements, and direct emails, some 73,000 activists have signed an online petition calling for an end to the industry tax breaks.

The DSCC, in a release, said it plans to use this issue against Republican Sens. Dean Heller (Nev.), Scott Brown (Mass.), Olympia Snowe (Maine) and Dick Lugar (Ind.), as well as Senate candidates including George Allen (Va.) and Reps. Denny Rehberg (Mont.), Jeff Flake (Ariz.) and Todd Akin (Mo.).

The petition, which will help the DSCC and Democratic campaigns expand their list of in-state activists, went live April 27. The online ads started running April 28, according to a DSCC spokesman.

Republicans are digging in over the issue of tax breaks for oil companies.

Senate Minority Leader Mitch McConnell (R-Ky.) said Sunday that Republicans won't discuss nixing the tax breaks as part of fiscal reform talks with Vice President Biden. 

"That's not the kind of thing we're going to be dealing with here in connection with the serious talks that are going on with the vice president's group," McConnell said on CNN's "State of the Union."

— Ben Geman contributed