Georgia’s pair of Senate runoffs this month will not only decide which party controls the Senate in the 117th Congress, but they also will crystallize the fight for the majority in the 118th.

The results of both Peach State races will determine whether Democrats kick off the cycle with 48, 49, or 50 seats— and how many seats either party must net to run the chamber come 2023.

After disappointing results left their majority hopes hanging by a thread, Democrats are optimistic they can buck traditional headwinds in 2022 thanks to the slate of states holding Senate elections. Historically, the ...