Johnny Isakson’s long upstream swim is coming to an end.

On Wednesday, the most enduring Republican politician in Georgia announced he will resign from the U.S. Senate on Dec. 31, just as a new year dawns on one of the most challenging election seasons faced by his GOP.

“It goes against every fiber of my being to leave in the middle of my Senate term, but I know it’s the right thing to do on behalf of my state,” the senator, 74, said in a statement.

Isakson has spent the August recess in Cobb County, coping with intense physical therapy after suffering four broken ribs in a fall last month at his Washington apartment. Surgery to remove a malignant growth on his kidney was conducted Monday. Recovery has been made more difficult by his bout with Parkinson’s disease, a progressive disease of the nervous system.

Finding a cure for Parkinson’s will become his cause in retirement, Isakson said.

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It will be up to Gov. Brian Kemp to name a replacement for Isakson’s seat in the Senate, who will then be on a special election ballot in November 2020. No doubt the replacement will be a Republican.

Whether he or she will be an Isakson Republican is another matter entirely. The senator has told associates that he intends to leave the choice entirely to Kemp — and will make no recommendations.

Moreover, Isakson’s position in the Georgia GOP is unique.

Through much of his 45 years in politics, Isakson has served as a counterpoint — in tone and style if not in substance — to a Republican Party that sometimes has been suspicious of his amicable relations with Democrats.

As the GOP made a hard-right turn in the 1990s, the party he helped give birth to in Georgia would nearly push him into permanent exile. Gov. Zell Miller, a Democrat and one-time foe, would bring him back to the great game when he appointed Isakson as chairman of the state Board of Education.

In his official U.S. Senate biography, Isakson notes that he’s the only Georgian ever to have been elected to the state House, state Senate, U.S. House and U.S. Senate. And he’s done it from beginning to end as a Republican — not as a Democratic convert.

In addition, in 2016 he became the first Georgia Republican ever to be elected to a third term in the U.S. Senate. Given the state’s changing demographics, and U.S. Sen. David Perdue’s promise to serve only two terms, that’s a record that could stand for some time.

“He always came at things from a conservative point of view. The longer he was in public office, I think the more pragmatic he became — because he was a doer,” former U.S. Sen. Saxby Chambliss said Wednesday. “He wasn’t going to throw bombs. There were enough people to do that.”

Chambliss, a lifelong friend of Isakson’s, retired from the Senate in 2015. The two more often than not voted in tandem.

“It wasn’t a matter of him moving to the center. It was a matter of him moving toward getting something accomplished,” Chambliss said. “Nobody has done that better than Johnny.”

In the chaotic climate of President Donald Trump’s administration, while several more of his Republican colleagues have abandoned the chamber, Isakson has kept his footing.

A former CEO who built his Northside Realty firm into the largest real estate operation in the South, Isakson has deftly maintained a cordial but arm’s length relationship with the real estate man in the White House, usually offering his support — but also calling out the author of “The Art of the Deal” when necessary.

In March, Isakson damned as “deplorable” Trump’s continued attacks on the late U.S. Sen. John McCain.

Nonetheless, Isakson will leave office as an anomaly in a hyperpolarized 21st century Washington, a conservative willing to work with Democrats and disdainful of shrill rhetoric.

One measure of his popularity: When Republicans took the Senate after the 2014 elections, his colleagues handed him two committee chairmanships. He heads up both the Senate’s Ethics Committee and Veterans Affairs Committee.

The former committee has required delicate, and often politically awkward, work behind the scenes investigating claims made against colleagues.

The VA assignment pitted Isakson against an institution long known for its woes, and one that was hit with a series of scandals during the Obama administration in Georgia and nationally. Last year, when Trump nominated Rear Adm. Ronny Jackson, a White House physician, as head of the U.S. Department of Veterans Affairs, Isakson was among those who quietly deep-sixed the nomination.

“If you had a vote in the Senate on who’s the most respected and well-liked member of the Senate, Johnny would win probably 100 to nothing,” Senate Majority Leader Mitch McConnell, R-Ky., an Isakson confidante, said earlier this year. “His demeanor is quite different from what most people expect of politicians.”

On Wednesday, Republicans were unstinting in their praise of Isakson in the wake of his announcement. U.S. Reps. Tom Graves of Ranger and Doug Collins of Gainesville counted him as a mentor.

More startling, especially in the current political climate, were the many Democrats who also spoke up. “His retirement is a great loss for the U.S. Senate and the people of this great state,” Atlanta Mayor Keisha Lance Bottoms said.

“Despite our disagreements on the important issues of today, I have always respected Senator Isakson for his work ethic on behalf of Georgia, and for his and his staff’s willingness to meet with any constituent, regardless of political leaning and regardless of the issue,” said U.S. Rep. Hank Johnson, D-Lithonia.

Johnson specifically noted Isakson’s steadfast appearances at Ebenezer Baptist Church on the Martin Luther King Jr. holiday.

The sentiment isn’t Johnny-come-lately. In 2016, former Gov. Roy Barnes — once the top Democrat in the state — took a great deal of criticism for endorsing Isakson’s Senate re-election bid. “If all Republicans were like Johnny,” Barnes once said, “I would be a Republican.”

Isakson’s political career began in 1974 when he ran for a county commission seat and lost. In 1976, he ran for a state House seat and won — even as the rest of the state voted big for Democrat Jimmy Carter in that year’s presidential contest. Isakson arrived at the Gold Dome along with fewer than two dozen Republicans.

He quickly established himself with his small band of Republicans, rising to the post of minority leader and using the position to occasionally take advantage of Democratic fractures along black-white, rural-urban lines.

“His ability to be a conciliator and a mediator I think was really born in that period of Republican Party history,” said Rusty Paul, a former chairman of the Georgia GOP. In the 1970s and ’80s, Republicans in the state Capitol weren’t necessarily the most conservative lawmakers in any room. With Paul Coverdell — another future member of the U.S. Senate — in a commensurate GOP leadership position in the state Senate, Isakson’s crew sometimes even referred to themselves as “progressives.” In a Theodore Roosevelt kind of way.

In 1990, Isakson took a first shot at higher office and ran for governor, losing to Miller in the general election.

In 1992, he won a state Senate seat.

Four years later in 1996, Isakson took another shot at statewide office, running for the U.S. Senate seat being vacated by Sam Nunn. This time, he lost the GOP nomination to businessman Guy Millner — who then lost to Democrat Max Cleland.

Isakson benefited from U.S. House Speaker Newt Gingrich’s misfortune after Republicans lost seats in the 1998 midterms, after impeaching President Bill Clinton.

Gingrich abruptly resigned his 6th District congressional seat. The majority of the district was then in Cobb, Isakson’s home turf.

In February 1999, in a special nonpartisan election, Isakson claimed his place in Washington. The quiet deal-maker replaced a quintessential bomb-thrower.

Isakson’s next step up came in 2004, when he won a U.S. Senate

primary contest against businessman Herman Cain and U.S. Rep. Mac Collins.

He then beat Democrat Denise Majette in the general election.

His deal-making style has been well suited to the clubby upper chamber. Isakson has formed alliances of all types, always eager to advance a parochial issue — such as Georgia’s “water wars” with Alabama and Florida or the expansion of the Port of Savannah.

He also has taken on issues that would become personal priorities. Compensation for U.S. hostages held in Iran at the end of the Carter administration has been one. Reform of U.S. Peace Corps policies that failed to prevent the murder of a volunteer from Georgia is another.

When President Barack Obama wanted to host Republican senators for dinner to chip away at his icy legislative relationships, he called Isakson to get them together.

Isakson has also been a popular traveling companion for Democratic lawmakers on fact-finding trips abroad. The associations sometimes raised eyebrows but also paid off. A trip to Greenland with one of the Senate’s most prominent liberals (the topic was climate change) produced a friendship that helped Isakson during a high-stakes “water wars” fight in 2013.

During tough policy debates, Isakson has often been cryptic about his positions, which gives him more space in which to negotiate.

Even though his votes still leaned conservative, some of Isakson’s biggest critics have been on the right — particularly when the tea party ascended as a political force in 2009.

Atlanta Tea Party founder Debbie Dooley once dismissed Isakson’s nonconfrontational approach to politics. Conservatives, she told The Atlanta Journal-Constitution, “want a Navy SEAL representing them. They don’t want Barney Fife.”

After the article saw print, Isakson had a “Barney Fife” nameplate made up for his office desk, promising to deploy it the next time Dooley visited. He had the good sense to decline a reporter’s request to be photographed with it.

When Republicans took control of the U.S. Senate in 2015, Isakson was tapped by McConnell to lead those two committees — a workload carried by no one else.

Despite his reputation as a bipartisan deal-maker, Isakson has been a steadfast party loyalist. He has been particularly vocal about his allegiance to McConnell, whose office he often visits unannounced.

“I’m on the team, and I’ll be doing what Mitch needs me to do,” Isakson told reporters two years ago, as he returned to Capitol Hill shortly after a pair of back surgeries — which set off early rumors of retirement.

By then, Isakson was already struggling with his Parkinson’s diagnosis. The public announcement explained his slow, shuffling gait, but it failed to slow the senator down, and his mental acuity has shown no signs of flagging. But a cane soon appeared in his hand. More recently, he’s traveled through the U.S. Capitol via wheelchair.

Parkinson’s and Trump arrived in Isakson’s world at roughly the same time. Each has been a challenge.

The senator has declined to defend many of the president’s more incendiary statements and policy proposals. Isakson pointedly criticized Trump’s comments after the white supremacist rally in Charlottesville in 2017 resulted in the death of a counterprotester.

More recently, Isakson voted with Democrats in January to end the longest federal shutdown on record, as negotiations with Trump’s proposed border wall reached a standstill.

“The fact of the matter is we’re not doing a damned thing while the American people are suffering,” Isakson said in a blunt speech on the Senate floor. “We’re just doing the wrong thing, punishing the wrong people, and it’s not right.”

Isakson’s approach to Trump and his history of campaigning in communities of color have been held up by some in the Republican Party as a model for GOP candidates struggling to hold onto their seats in Atlanta’s fast-changing suburban districts.

In 2016, Trump won 51.05% of the vote in Georgia. Isakson won 54.8%.

But even Isakson’s closest allies acknowledged that he has been among a shrinking group within the party. “It’s not the in-vogue mentality right now,” Heath Garrett, Isakson’s longtime political strategist, said in February. “It’s easier to just listen to Rush Limbaugh and be the most conservative person and win a really easy Republican district.

“But I sure hope that there are more Johnny Isaksons out there — and I think that there are.”

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