From the Economist(soft paywalled)
The well-respected senator, who said he was stepping down because of “mounting health challenges”, would not otherwise have been up for re-election until 2022, when he would probably have kept his seat.
The author was describing a future unreal event. According to what I learned in high school, he should have used present conditional instead of perfect conditional, which is used to describe unreal events in the past.
The well-respected senator....otherwise would not be up for re-election...when he would probably keep his seat.
I always find conditionals very hard to grasp while learning English. I don't know if I made a mistake or if the venerable TE did. Thanks for your time.