WASHINGTON — Facing health challenges, Republican Senator Johnny Isakson of Georgia said Wednesday that 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 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 .
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 walking through the corridors at the Capitol with a noticeably slower, shuffling gait.
He disclosed the diagnosis in 2015 while gearing up to seek a third term, but kept up a schedule in the Senate. He was often seen as a moderating influence, willing to reach across the aisle at a time of deep partisanship.
After winning reelection, he underwent a scheduled surgery in 2017 on his back to address spinal deterioration. At times, he has been in a wheelchair.
In July, Isakson was hospitalized after fracturing four ribs in a fall at his Washington apartment.
He spent nearly a week recovering in a Georgia rehabilitation facility.
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 term.
Isakson will step down in December.
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.