Tester has been attacking his opponent for months over the lawsuit. Rehberg sued the city of Billings, Mont., after a wildfire devastated his land. Tester’s ad contends the lawsuit, which was dropped, cost the city thousands of dollars in legal fees.

“The congressman sure doesn’t take responsibility for anything,” says Tim Bergstrom, a retired Billings firefighter.

The ad goes on, “The lawsuit was dropped because it had no merit, but not before costing us tens of thousands in legal fees, which should have been spent on libraries and police instead. Congressman Rehberg needs to start taking responsibility for his own behavior, because Montanans are paying the price.”

Tester and Rehberg have been locked in a tough race throughout the year. Rehberg has maintained a slight lead throughout, topping Tester 46 to 43 percent in the RealClearPolitics average.

Tester reported raising $2.3 million in the third quarter, his largest haul to date, and ended with $1.3 million cash on hand, according to The Associated Press. Rehberg has not released his fundraising numbers.

In another ad, the DSCC blasts Rehberg for the lawsuit, which the DSCC says cost the city $21,000.

“Wildfires. They destroy homes and lives. Firefighters put themselves on the line every day,” a narrator says. “But instead of thanking them, Congressman Dennis Rehberg filed a lawsuit against the fire department, blaming firefighters for damage on his property.

“Dennis Rehberg. He’s for himself, not us.”