How will U.S. Sen. Johnny Isakson’s replacement be chosen?

Voters will get their say on a longer-term replacement for Republican U.S. Sen. Johnny Isakson during a wide-open special election in November 2020, when they’ll also cast ballots for president.

After Isakson steps down at the end of this year, Republican Gov. Brian Kemp will appoint a senator to serve in Washington until the special election.

Then candidates from all political parties will compete against each other in November, creating the possibility of many candidates in one race and the likelihood of a runoff Jan. 5, 2021. A runoff is required if none of the candidates receives a majority of votes. There will be no primary election for the Senate seat.

>> Photos: Johnny Isakson through the years

>> Timeline: Key moments in Johnny Isakson's public life

>> 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.