Johnny Isakson began a chain reaction destined to remake the state Capitol power structure with a surprise announcement Thursday that he will seek re-election to the U.S. Senate in 2010 rather than run for governor.

Isakson's decision to stay in Washington means Georgia could — depending on how many Republicans enter the sweepstakes to replace Sonny Perdue — have a new governor, lieutenant governor, secretary of state, insurance commissioner, a few new congressmen and new state legislative leadership by January 2011.

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Johnny Isakson

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"Johnny just fired the open gun for the governor's race," Rusty Paul, former state Republican Party chief, said after hearing of Isakson's decision. "It's going to be a free-for-all."

Isakson spokeswoman Joan Kirchner said the senator told his staff of his decision during a morning meeting.

"Johnny loves serving in the U.S. Senate, and he thinks this presidential election — no matter who wins — will be one of the most important in the country's history," Kirchner said. "And in the next administration, the U.S. Senate will be where all the action is."

The announcement by Isakson, 63, likely means the popular Republican stalwart, who once served in both the state Senate and House, is likely to finish his long political career in Washington. If re-elected to the U.S. Senate in 2010, he would be in his early 70s by the time his next term ended.

Perdue will be completing his second term as governor in 2010 and cannot run for re-election.

Word of an effort to persuade Isakson to give up his Senate seat for the Governor's Mansion, originating with the state business community, began last spring.

Other Republicans had shelved their ambitions to wait for Isakson's decision.

"Had he decided to come home and run for governor, he would have cleared the field on the Republican side. He would have been the clear favorite," said House Majority Leader Jerry Keen (R-St. Simons Island). Keen is now considering the race.

Isakson won his party's nomination for governor in 1990, only to be bested by Zell Miller.

Heath Garrett, former longtime chief of staff for Isakson, said Isakson wasn't nostalgic for a second attempt.

"Johnny's inclination was never to run for governor, but he did get enough pressure and enough people of substance asking him to consider it, that he did give it serious consideration," Garrett said.

"But he also didn't feel that this decision ought to be dragged out."

Isakson's decision comes a week before the state GOP convention and is sure to send an army of hopefuls to Columbus.

In addition to Keen, potential GOP candidates to replace Perdue include Lt. Gov. Casey Cagle, Secretary of State Karen Handel and U.S. Reps. Lynn Westmoreland and Jack Kingston. Insurance Commissioner John Oxendine announced in April that he'd give up his job for a shot at governor.

House Speaker Glenn Richardson's name also has been mentioned, but many political experts doubt he'll run. Richardson was out of town Thursday and could not be reached for comment.

Each hopeful who joins the race would create a vacant position, likely attracting legislative leaders wanting to move up.

The last time the governor's and lieutenant governor's posts were both vacated — without an incumbent running for re-election — was in 1998, when Miller and Lt. Gov. Pierre Howard left office together.

Democrats concede Isakson's bipartisan appeal, and some said his announcement might persuade them to enter the race for governor as well.

House Minority Leader DuBose Porter (D-Dublin) said he will likely decide after the fall elections.

"Johnny and I have a lot of the same business friends, and this will make it easier for some people not to be caught in the middle," said Porter, who served with Isakson in the state House.

Republicans on Thursday were effusive in their praise for Isakson but were reluctant to discuss their own ambitions.

"There will be plenty of time over the course of the next few months to speculate and sort things through," Handel said. A spokesman for Westmoreland expressed similar sentiments.

Cagle, just back from an overseas trip, was unavailable for comment, his spokeswoman said.

Oxendine said with Isakson out of the governor's race, he becomes the best-known candidate because he has won statewide races four times.

"I think it is definitely quite beneficial to our campaign," Oxendine said.

One disappointed figure is Kessel Stelling, president and CEO of the Bank of North Georgia. He was among those urging Isakson to come home. "And I was urging others to urge him as well," Stelling said.

For the past two years, sessions of the General Assembly have devolved into slugfests among Perdue, Cagle and Richardson. Business leaders saw major issues — transportation and traffic congestion in particular — shoved to the side.

Garrett, Isakson's former aide, said the senator was getting calls from both Republicans and Democrats asking him to run for governor.

But Garrett added, "When it was all said or done, when every argument and counterargument was laid out on the table, it all boiled down to the fact that he really sees an equal value in being a United States senator .... and being the chief executive of the state on domestic policy.

"He really is at peace with his role as a United States senator and, hopefully, after re-election, for one more term," he said.

Stelling said he accepts Isakson's decision and will continue to support him. But massive issues facing metro Atlanta and Georgia require that the search for a suitable candidate for governor continue, he said.

"I think the entire business community needs to sit back and reflect," Stelling said. "It's got to be someone who can not only bring together one party, but even reach out to the other side."