Republican Sen. Johnny Isakson announces he will retire at the end of the year

Sen. Johnny Isakson (R-Ga.) announced Wednesday that he will retire at the end of the year.

Here's what we know

In a Wednesday morning statement, the 74-year-old Isakson said that he had made his decision "[a]fter much prayer and consultation with my family and my doctors." Isakson has faced several health issues, including Parkinson's disease. This week he also had a renal cell carcinoma removed from his kidney.

"In my 40 years in elected office, I have always put my constituents and my state of Georgia first," he wrote. "With the mounting health challenges I am facing, 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. 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."

The senator was most recently reelected in 2016 with 54% of the vote. Georgia Gov. Brian Kemp (R) will need to appoint someone to replace Isakson until a special election can be held next November for the remainder of Isakson's term. Georgia's other U.S. senator, David Perdue (R), will also be up for election that same year. Whoever wins the special election to replace Isakson will be up for reelection in 2022.

Former Georgia Democratic gubernatorial candidate Stacey Abrams said she will not be running for Isakson's seat, instead focusing on "voter protection efforts in key states across the country."

What else?

Isakson has been in the U.S. Senate since 2004, when he replaced Zell Miller, the blue dog Democrat who once challenged MSNBC host Chris Matthews to a duel on air.

According to his retirement announcement, Isakson was "the only elected official in Georgia to serve in the Georgia House, the Georgia Senate, the U.S. House and the U.S. Senate."