‘You’re screwed’: Romney’s exit threatens a collapse of Senate’s middle

Mitt Romney’s retirement shines a glaring spotlight on the potentially bleak future of the Senate’s ideological center in both parties. If Joe Manchin and Kyrsten Sinema follow him out the door, it will get worse.

Manchin, a centrist Democrat, and the Independent Sinema are both still mulling whether to run again. Like Romney, they could be replaced by senators on either end of the ideological spectrum — almost surely a Republican in Manchin’s West Virginia.

And as maligned as Romney, Manchin and Sinema are by one party or the other’s...