Ron Crumpton, who had declared himself a candidate for the U.S. Senate race, announced Tuesday that he is withdrawing.

Crumpton, a Democrat from Talladega who is executive director of Alabama Patients' Rights Coalition, cited a back injury as the reason he will not compete in the special election.

With Crumpton's withdrawal, the remaining Democrats who have announced as candidates are former U.S. attorney Doug Jones of Birmingham and Robert Kennedy Jr. of Mobile.

Crumpton, who said he has a long history of back problems, will require weeks of doctor-advised recovery after his latest setback.

Crumpton ran against U.S. Sen. Richard Shelby last year, receiving 36 percent of the vote.

State Auditor Jim Zeigler also said Tuesday he is not running for Senate, though he never declared for the race.