Attorney General Jon Bruning (R-Neb.) went on the air this week with an advertisement hitting Sen. Ben Nelson (D).

“There are big differences between Ben Nelson and me,” Bruning says in the straight-to-camera clip. “Here’s one: Ben Nelson was the deciding vote to pass Obamacare. Ben even fought for the embarrassing Cornhusker Kickback.”

Bruning’s spot is the latest shot in the early ad war in the highly competitive Senate race. Democrats have spent more than $1 million this year pumping Nelson in media spots, and conservative independent groups have already invested more than half a million dollars in negative advertisements against the two-term Democrat.

Bruning is the first Republican challenger to air ads. State Treasurer Don Stenberg and state Sen. Deb Fischer are also running, and Gov. Dave Heineman hinted this week that he might take a second look at the race.

Bruning’s advertisement will run statewide on cable for a “couple weeks of initial advertising,” according to Bruning’s campaign manager, Trent Fellers.