U.S. Sen. Russ Feingold, D-Wisconsin, responded to former Gov. Tommy Thompson's potential run for Senate Tuesday in an e-mail to supporters.
""It's very likely that former Bush administration HHS Secretary Tommy Thompson will enter the Republican primary to run against me in November,"" Feingold said in the message.
On March 7, former Thompson aid Bill McCoshen said Thompson has been considering a campaign for the seat.
""I wouldn't expect to see an announcement from him until the Republican convention on May 20th,"" McCoshen said on ""Up Front with Mike Gousha."" ""But you're going to see additional evidence shortly that this thing is ramping itself up, that there are serious people involved in this effort and that Tommy is very seriously considering it.""
John Kraus, Feingold campaign spokesperson, said they would not change their strategy but welcomed the competition if Thompson decided to enter the race.
He said Feingold's grassroots efforts and careerlong fight against lobbyists in Washington will help him win the race in November.
""Voters are going to have a really clear choice in this election if Secretary Thompson decides to get in the race,"" Kraus said.
The recently passed health-care bill would also be a divisive issue in a potential campaign.
Kristin Ruesch, spokesperson for the Republican Party of Wisconsin, said Feingold's vote in favor of the bill will hurt him in a campaign in which he is already vulnerable.
""Feingold ignored the wishes of the majority of Wisconsinites when he voted for the health-care legislation,"" Ruesch said.
However, according to UW-Madison political science professor David Cannon, the passage of the health-care bill may help Democrats, including Feingold, retain seats in the 2010 elections. He said it demonstrates that the Democrats can accomplish their goals.
Cannon also said Thompson's name recognition and popularity during his time as governor will help him, while Feingold's strength lies in his record of independence and constituency outreach efforts.
All agreed that a potential race between Thompson and Feingold promises to be very competitive.
