APPLETON, Wis. (WTAQ) - Former U.S. House Democrat Steve Kagen of Appleton is the latest to say he’s thinking about running for Herb Kohl’s Senate seat next year.

Kagen served for four years in Washington before losing to Republican Reid Ribble last November.

Kagen said he’s seriously thinking about adding his name to a large field of possible candidates for the state’s first open U.S. Senate seat in two dozen years. He did not give a timetable on a decision.

Also on the Democratic side, Milwaukee Mayor Tom Barrett’s campaign confirmed Tuesday that he won’t run.

Other Democratic possibilities are House members Ron Kind of La Crosse and Tammy Baldwin of Madison.

On the Republican side, Tommy Thompson aide Jason Denby confirmed that his boss is thinking about a Senate bid. But the former governor is in Japan this week, and he won’t be making any quick decisions.

House Budget Chairman Paul Ryan says he won’t run for Kohl’s seat. Former House Republican Mark Neumann says he’s still interested, as are legislative leaders Scott and Jeff Fitzgerald.