The final Senate retirement questions were answered over the weekend, with both South Dakota's John Thune and Wisconsin's Ron Johnson deciding to run for re-election in 2022. That leaves Republicans with five open seats (Pennsylvania, North Carolina, Ohio, Missouri and Alabama) and Democrats with one (Vermont).

The two incumbent senators could hardly be more different. Thune is the clear favorite to succeed Mitch McConnell one day as GOP leader. His hesitance to run again seemed to stem with the direction of the Republican Party under former President Trump (though efforts to find a viable Trump-inspired primary challenger floundered early on).

Johnson, meanwhile, has embraced Trump and has spouted conspiracy theories in the wake of January 6 and about COVID treatments and vaccines. Democrats are eager to take on the polarizing two-term senator after he broke his self-imposed term limits pledge in a perpetual battleground state that is nearly evenly divided. Still, Johnson finds himself in a better position than last summer when we moved this race into Toss Up. He remains the only incumbent running in a

More from the Cook Political Report