The surprise announcement immediately scrambled the crowded contest to replace Gov. Sonny Perdue when his second term expires in 2010. Cagle was considered a front-runner for the Republican nomination with the primary still more than one year away. The 43-year-old Republican from Gainesville said he will seek re-election as lieutenant governor.

He explained that he's had pain in his left shoulder for several years but that it worsened during this year's legislative session and spread to his spine and breastbone. Eventually he began to experience paralysis in his left arm and went to see a doctor.

"I have a very serious issue to my neck, along with my spinal area, that has caused nerve damage that will need to be repaired," Cagle said at a state Capitol news conference where he was flanked by his wife and three sons.

A neurologist recommended surgery, he added.

Cagle called the decision to drop his gubernatorial bid "difficult personally for me."

"This is a challenge that I have to face and I will come through it," Cagle said of his health problems.

Cagle declined to answer questions following his brief remarks.

A spokeswoman refused to provide more details about his condition or the surgical procedure he would undergo, except to say that it would require "a significant recovery period."

"We're not going to share, at this time, a specific diagnosis but it is serious enough that he wants to take the time to care for his health first," Jaillene Hunter said.

Hunter would also not elaborate on why Cagle felt he could handle the lieutenant governor's race but not the one for governor. Both are statewide contests.

"He does feel up to running for lieutenant governor," Hunter said.

Cagle's withdrawal from the race leaves three Republicans still in the field: Secretary of State Karen Handel, Insurance Commissioner John Oxendine and state Rep. Austin Scott, of Tifton.

Handel said she was "saddened" to hear about Cagle's health and his withdrawal from the race.

"I hope his health issue is resolved quickly," she said in a statement.

Oxendine said he considered Cagle "a friend" and an "honorable opponent."

He also issued a call for support from Cagle's backers

"I would consider it an honor to earn the support of my fellow Republicans who had initially chosen to support Casey Cagle," Oxendine said.

Scott could not immediately be reached for comment.

Cagle had raised the most money so far and his withdrawal could attract other GOP candidates to the contest, including Cobb County Commission Chairman Sam Olens.

On the Democratic side, Attorney General Thurbert Baker, House Minority Leader DuBose Porter and former Georgia National Guard Commander David Poythress have thrown their hats in the ring for governor. Former Gov. Roy Barnes is also considering the contest.

Cagle was elected lieutenant governor in 2006, the first Republican it win the seat in Georgia. A relative unknown, he won the seat after upsetting former Christian Coalition head Ralph Reed in a GOP primary.

Before taking over as the state's No. 2, Cagle served 12 years in the state Senate.

Cagle's decision to seek re-election as lieutenant governor complicates that race as well. Republican State Sens. David Shafer, of Duluth, and Eric Johnson, of Savannah, were set to face off to replace Cagle.

Both men on Wednesday wished Cagle a speedy recovery.

Shafer said that "we are reevaluating our options in light of his decision."

Johnson noted that "the election is still a long way off and circumstances could continue to change."

"In the meantime, we will keep our options open," he said.