Until the morning of June 10, next year’s U.S. Senate race appeared to be already settled.

Incumbent Sen. Johnny Isakson, one of the most likeable people in state politics over the past four decades, is running hard and gathering up gobs of money in the process — he raised more than $1.6 million during the first quarter to bring his campaign account balance to nearly $4 million.

Isakson’s only announced primary opponent so far is a fringe candidate who served time in prison on a felony conviction and got 1 percent of the vote in last year’s Senate race to replace Saxby Chambliss.

No Democrat has hinted at running next year against the popular senator. If there was anyone with an easy path to reelection, it seemed to be Isakson.

But then, Isakson’s office made the surprise announcement that he was suffering from Parkinson’s disease, a progressive disorder of the nervous system that affects a person’s movement and causes tremors and shaking. The actor Michael J. Fox has been afflicted with Parkinson’s for several years.

“Parkinson’s disease symptoms worsen as your condition progresses over time,” according to the Mayo Clinic. Even so, Isakson still intends to maintain his campaign for a third term.

“I remain devoted to public service, to my state and to my constituents,” he said. “I am eager to take my record of results to the voters of Georgia as I run for re-election in 2016.”

Isakson has had other medical problems in recent years. In 2010, as he was preparing for that reelection campaign, he was hospitalized twice and spent time in an intensive care unit for an irregular heartbeat and a blood infection.

“I nearly bought the farm,” he acknowledged to me after he recovered from those maladies and won reelection.

Isakson had back surgery last October and fractured three ribs earlier this year, which his staff said was the result of an accident while moving household furniture. He is dealing with the kinds of medical issues that typically confront people as they move into their 70s.

Now that he has disclosed he’s in the early stages of Parkinson’s, we can understand why Isakson announced his reelection intentions so early and devoted so much time and energy to fundraising. He wanted to do as much as possible to scare off any opposition before revealing the diagnosis.

His situation is similar to that faced by another esteemed Georgia politician who held this same Senate seat nearly 60 years ago.

In 1956, Walter F. George was making plans to run for a seventh term in the U.S. Senate. He was a Washington insider and a favorite of the state’s business community, but George was 78 years old and had a heart condition that would, in fact, kill him in 1957.

Herman Talmadge, who had just finished serving six years as governor, declared he would run for George’s Senate seat. Even though George was a venerated figure in political circles, some of the business leaders who had supported him in the past became reluctant to continue that financial backing.

George soon determined that he wouldn’t be able to stand up to the rigors or a statewide campaign against a much younger opponent and withdrew from the race, handing over the Senate seat to Talmadge.

Isakson is also a favorite of Georgia’s business establishment, which has helped him amass that $4 million in contributions for this campaign. In light of his medical condition and his age, will they continue to pump money into Isakson’s coffers?

No credible challenger has yet indicated they will take on Isakson in 2016, but it will be interesting to see how long that situation holds.

Will another Republican take up the role of Herman Talmadge and oppose Isakson in the GOP primary? Will some Democrat, perhaps a former congressman like John Barrow, decide that Isakson’s medical issues could make him a little more vulnerable in a presidential election year where Democratic voter turnout is usually higher?

This has become a campaign to keep your eye on. Isakson is in good shape financially, is certainly well-liked by voters, and is not facing any credible opposition right now. I have a feeling that this race could become a little more crowded.

Tom Crawford is editor of The Georgia Report, an Internet news service at gareport.com that reports on state government and politics. He can be reached at tcrawford@gareport.com.