>> Related: Georgia's Isakson to resign from Senate at end of 2019
The winner will serve the remainder of Isakson’s six-year term, which ends in 2022, and then another election will be held for a full term.
A similar special election played out in 2017, when 18 candidates ran to replace former U.S. Rep. Tom Price, whom President Donald Trump appointed as secretary of U.S. Department of Health and Human Services.
That high-profile race went to a runoff, when Republican Karen Handel defeated Democrat Jon Ossoff.
Republican U.S. Sen. David Perdue will also be on the ballot in 2020, along with the winner of the Democratic Party primary. Three Democrats are already in the race: former nominee for lieutenant governor Sarah Riggs Amico, Clarkston Mayor Ted Terry and former Columbus Mayor Teresa Tomlinson.