Associated Press File Photo / U.S. Sen. David Perdue, R-Georgia, will be up for re-election in 2020, but will have to share the stage with a special election to fill the unexpired seat of retiring Sen. Johnny Isakson.

Georgia voters will have an opportunity next November that hasn't come their way in more than 100 years.

When Republican U.S. Sen. Johnny Isakson, 74, said last week he'd step down at the end of this year due to health reasons, it set up the Peach State to have two senatorial races in 2020.

U.S. Sen. David Perdue, a Republican, also will be seeking his second term.

An election with two U.S. Senate races in the same year in Georgia hasn't occurred since 1914. In that year, Democratic Sen. M. Hoke Smith was elected to a second term, and Thomas W. Hardwick was elected to fill the unexpired term of Augustus Octavius Bacon, who died in office.

Tennessee voters had such an opportunity in 1994. Fortuitously for Republicans, the year happened to be one in which voters were angry at Democrats over events in the Clinton presidential administration, including the attempted federal takeover of the health care system.

That year, Nashville surgeon Dr. Bill Frist, a Republican, upset three-term Democratic Sen. Jim Sasser, and actor and attorney Fred Thompson, a Republican, defeated Democratic U.S. Rep. Jim Cooper.

Republicans went on to win a net eight Senate seats and 54 seats in the U.S. House that year, and no Democrat has been elected to the Senate from the Volunteer State since.

In Georgia, with two seats available, Democrats hope to win their first Senate seat since 2000 in what they believe is a state moving back from red to blue.

Republicans will need to think strategically about how to place themselves in the best opportunity to keep both seats.

Perdue, who won his first term by nearly eight percentage points over Democrat Michelle Nunn (daughter of former Democrat Sen. Sam Nunn) in a race pundits thought would be razor close, is thought to be a favorite for re-election. His Democratic opponents so far include a former Columbus mayor, a former lieutenant governor candidate and the current Clarkston mayor.

His opponents hope to tie him to President Donald Trump, who is hated by Democrats and is not held in high regard by some suburban Atlanta voters who might otherwise vote for Republicans.

Isakson, less chummy with the president and said to be well-liked across the aisle, was elected with more than 54% of the vote to his third term in 2016, becoming the first Georgia Republican to win a third Senate term.

"He's a gentleman who's spent his career looking for common ground," said U.S. Sen. Mark Warner, D-Virginia, "and actually trying to accomplish something in Washington."

Democrats tried to recruit 2018 Georgia gubernatorial loser Stacey Abrams to make the race against Perdue, but after much dithering, she decided against it. A spokesman for Abrams said last week she would not run for Isakson's seat, either.

Republican Gov. Brian Kemp will have the opportunity to fill Isakson's seat but will need to decide whether to appoint someone who would run for the remainder of Isakson's seat in the fall or be a seat-filler until the election. Either way, it's likely to be a Republican. The winner of that election could then choose to run for a full six-year term in 2022.

An appointee who would run in 2020 may be seen by some voters as being given an unfair leg up in the race, but an appointee also would have the advantages of incumbency.

Potential Republican candidates include U.S. Rep. Doug Collins, Georgia Attorney General Chris Carr, Lt. Gov. Geoff Duncan and Georgia Senate Pro Tem Butch Miller. Tweets also have touted Herman Cain, the former Godfather's Pizza CEO and former Federal Reserve Board nominee.

Democrats mentioned as possibilities include Nunn, 2014 gubernatorial loser Jason Carter, former congressional candidate Jon Osoff and the Rev. Raphael Warnock, pastor of Atlanta's Ebenezer Baptist Church.

The special election vote for Isakson's seat in November 2020 will not feature a Republican and a Democrat chosen in summer primaries but will be a "jungle" primary, with the top two finishers (unless one receives 50% plus one vote) of either party vying in a likely early December 2020 runoff.

That December race potentially could decide control of the Senate, which will be critical no matter who is elected president. Republicans currently have a 53-47 seat advantage. If Democrats were to pick up a net of three seats in November — not likely at the moment — the possible runoff for Isakson's seat would take on even bigger implications.

But a lot can happen between now and then. Stay tuned.