Let the political ad battle begin...

WASHINGTON, Nov. 17 (UPI) -- Ad wars among outside interest groups have begun in several U.S. congressional races -- about a year before Election Day.

Television spots underwritten a coalition of labor groups urge Montana Rep. Denny Rehberg, Nevada Sen. Dean Heller and Massachusetts Sen. Scott Brown, all Republicans, to protect Medicare, while the Chamber of Commerce launched an ad critical of Democratic Sens. Sherrod Brown in Ohio and Jon Tester in Montana for their stances on several issues, Politico reported Wednesday.

A spokeswoman for Americans United for Change, one of the union coalition sponsors, didn't reveal the size of the buy but said the ads would run as the congressional supercommittee begins its final week of negotiations to work out a deficit reduction deal by Thanksgiving.

The Chamber's total ad buy is estimated to be about $1 million, Politico said. The group said it plans to target about a dozen Senate races and at least 50 House seats.