With Kohl's Retirement, Wisconsin Vaults to the Top of Contentious 2012 Senate Races

U.S. Sen. Herb Kohl, D-Wis. speaks at a news conference Friday, May 13, 2011, in Milwaukee. Kohl said he has decided not to run for re-election after serving in the U.S. Senate since 1989. (AP Photo/Morry Gash)

There's a new big dog among the top 2012 U.S. Senate races.

With Friday's retirement announcement by Sen. Herb Kohl, D-Wis., the Badger State has suddenly become the focal point in the next election as it plays host to what could be America's most contentious Senate race.

The recent battle between Republican governor Scott Walker and public labor unions over limits on collective bargaining rights set the political table in Wisconsin and with Kohl retiring, there's no doubt both Republicans and Democrats see the seat as a place to plant a victory flag. Since potential Senate candidates took sides in the high-profile, rhetoric-filled showdown, some will see the race as a referendum on Walker's new law.

And both parties could bring out their own big dogs to battle for the open seat.

If he decides to run, former Democratic Senator Russ Feingold, who was swept out of Washington in the same 2010 tidal wave that swept Governor Walker into Madison, would instantly give Democrats a serious shot at holding on to the seat. Calls for Feingold to enter the race have already begun with some groups starting online petitions.

"We need Russ Feingold," says an email from the left-wing group 21st Century Democrats. "Sign our petition to draft Russ Feingold today. We'll be sending him this petition to show him how important it is that he runs for Senate in 2012."

House Budget Committee Chairman Paul Ryan, R-Wis., who has risen to prominence as a fiscal hawk in a time when fiscal conservatism is all the rage would immediately bring a level of Republican star-power to the race. And Ryan is clearly considering the idea.

"I was surprised by Senator Kohl's announcement and want to take some time over the next few days to discuss this news with my family and supporters before making any decision about how I'm best able to serve my employers in the First Congressional District, our state and nation," Ryan said in a statement.

The National Republican Senatorial Committee (NRSC) noted the state's political climate and pointed back to Feingold's 2010 loss when predicting the GOP would pick up Kohl's Wisconsin seat in 2012.

"As Russ Feingold discovered last year, whomever the Democrats eventually nominate, he or she will have a very tough time selling Wisconsinites on the Washington Democrats' agenda of reckless deficit spending, massive debt, and job-killing tax hikes," NRSC Spokesman Brian Walsh write in a statement. "Wisconsin continues to be a prime pickup opportunity for Senate Republicans in 2012."

Governor Scott Walker could throw himself in the race but after being battered and bruised in last winter's battle with big labor, his name is a lightning rod of Wisconsin politics.

Wisconsin joins Montana, North Dakota, West Virginia and Virginia as states in which Democrats will likely struggle most to maintain Senate seats. With incumbents who rode into office on a 2006 wave of anti-Bush sentiment, and a new national focus on fiscal conservatism, these traditionally Republican states are likely to be some of the most closely contested races in the nation.

But with an open seat and a statewide battle between government and labor that is a microcosm of the national narrative, Wisconsin's Senate race could now prove to tightest and most testy of them all.