The Associated Press

WASHINGTON — Facing health challenges, Republican Sen. Johnny Isakson of Georgia said Wednesday he will retire at year’s end, a departure that sets up a rare election in November 2020 when both of the state’s Senate seats will be on the ballot.

The affable 74-year-old lawmaker said he is leaving the job he loves because “mounting” health issues, including Parkinson’s disease, are “taking their toll” on his work, family and staff. He won a third term in 2016 and would have faced re-election in 2022 if he had run again.

“I have concluded that I will not be able to do the job over the long term in the manner the citizens of Georgia deserve,” Isakson said in a statement. “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.”

Isakson, who plans to return to Washington when the Senate resumes next month, was diagnosed in 2013 with Parkinson’s, the chronic and progressive movement disorder often left him moving through the corridors at the Capitol with a noticeably slower, shuffling gate.

He disclosed the diagnosis in 2015, while gearing up to seek a third term in the Senate, but kept up a schedule in the Senate, where he was often seen as a moderating influence, willing to reach across the aisle at a time of deep partisanship.

After winning re-election, he underwent a scheduled surgery in 2017 on his back to address spinal deterioration. At times, he has been in a wheelchair.

Then in July, Isakson was hospitalized after fracturing four ribs in a fall at his Washington apartment and spent nearly a week recovering in a Georgia rehabilitation facility.

He said Wednesday that he looks forward to returning to the Capitol in September and plans to continue helping those who are “working toward a cure for Parkinson’s.”

Georgia Gov. Brian Kemp, a Republican, said he would appoint Isakson’s replacement “at the appropriate time.” The senator will step down in December.

The ballot in November 2020 will now feature a special election for the remaining part of Isakson’s term as well as the regular election for the Senate seat now held by Republican David Perdue, who is seeking a second six-year term.

Republican strategists were suggesting that former White House official Nick Ayers, who returned to Georgia, could be considered for the appointment. Other Republicans, including statewide elected officials and members of Congress, including Reps. Doug Collins and Tom Graves, could be seen as candidates.

One prominent Democrat, Stacey Abrams, “will not be a candidate,” a spokesman said on Twitter. Abrams, who was being wooed to run against Perdue, will continue to focus on voter access issues in Georgia and across the nation.

The seat is expected to lean Republican, but Georgia remains in Democrats sights as a changing electorate provides openings.

Isakson’s political career spanned 40 years in Georgia politics, where he made millions in a real estate.

In 1990, he lost the race for governor to Democrat Zell Miller. His political career received a jump start when in 1998 U.S. House Speaker Newt Gingrich decided not to seek re-election. Isakson won a 1999 special election to fill the suburban Atlanta seat. Isakson won the Senate seat in 2004.