Oakland County Sheriff Michael Bouchard has dropped out of the US Senate race.
The 48-year-old Republican says health problems recently became known that make it unwise to begin a strenuous campaign.
Bouchard entered the race last week and says he's extremely disappointed to have to withdraw.
He says the health problems are not life-threatening and should not keep him from carrying out his sheriff's duties.
Industrial engineer Bart Baron of Troy is the only Republican officially in the race to take on Democratic US Senator Debbie Stabenow of Lansing.
Others Republicans considering a run in 2006 are Jane Abraham, Detroit real estate developer Peter Cummings, Oakland County Prosecutor David Gorcyca and the Reverend Keith Butler of Southfield.