Businessman Ron Johnson (R) appears to be just about ready to announce a challenge to Sen. Russ Feingold (D).

Paperwork on file in the Senate’s public records office shows that he has filed a statement of candidacy and organized a campaign committee. In addition, WisPolitics.com reports Johnson has hired his senior campaign staff. He’s expected to announce his campaign before the state GOP convention May 21-23.

Johnson, who has ample personal wealth, is entering a Republican race that includes real estate developer Terrence Wall and small-business man Dave Westlake, who have been campaigning for months, as well as Dick Leinenkugel, a former brewing company executive who entered the race last month.