Former Rep. Mark Neumann announced Monday that he is running for Wisconsin’s open Senate seat, setting up a likely GOP primary battle with former Gov. Tommy Thompson.

“We are going to enter the race for the United States Senate,” Neumann said Monday morning on WTMJ-AM in Milwaukee.

Neumann, who is the first major candidate to enter the race, said he will be announcing his campaign team in the next few weeks, adding, “We’re off and running.”

Despite speculation of a bitter primary with Thompson and other Republicans, Neumann said his campaign plans to focus on how to balance the federal budget and on the likely Democratic nominee, Rep. Tammy Baldwin. Another potential GOP primary foe is state Assembly Speaker Jeff Fitzgerald, who said last week he is likely to enter the race as well.

Thompson, who has yet to make his campaign official, is already being bombarded with TV ad attacks by the conservative Club for Growth, where some of Neumann’s former Congressional staffers work. But Neumann denied any collusion with the political action committee and declined to criticize Thompson.

“Tommy Thompson deserves our respect in this state … and that’s where Mark Neumann is going to be coming from,” Neumann said.

However, Neumann said, “I would hope the Club for Growth would support my candidacy. We need all the help we can get to beat Tammy Baldwin.”

Neumann is coming off an unsuccessful bid for governor last year, losing in the GOP primary to now-Gov. Scott Walker. After losing a special House election in 1993, Neumann was elected in 1994 to his first of two terms in Congress. He gave up his seat in 1998 to run for Senate, losing to then-Sen. Russ Feingold (D).

Feingold, who lost his re-election bid last year, announced this month that he would not seek the seat of retiring Sen. Herb Kohl (D). That leaves Baldwin as the likely nominee, although Rep. Ron Kind (D) is still considering a bid.