Updated

Wisconsin state Assembly Speaker Jeff Fitzgerald is planning to run for the U.S. Senate, but likely won't make it official until October.

Fitzgerald spokesman John Jagler said Tuesday that he fully expects Fitzgerald to enter the race, but "there is no formal announcement until he takes the steps necessary to make it official."

Fitzgerald has been saying that he intends to run, but he has yet to organize a campaign committee or take other necessary steps to launch a campaign.

On Monday, former Republican U.S. Rep. Mark Neumann became the first candidate to formally announce his candidacy. A number of others, including former Gov. Tommy Thompson, are seriously considering it.

The seat is being vacated by Democrat Herb Kohl, who is retiring.