Is tight Kentucky governor’s race a sign of trouble awaiting McConnell in 2020?

Shortly before Kentucky Gov. Matt Bevin won his first term four years ago, he made an elaborate show of contrition to onetime rival and fellow Republican Mitch McConnell, showing a satirical video at a GOP dinner in which Bevin appeared to get a McConnell-themed tattoo.

Now Bevin is in the homestretch of a bitter reelection battle — against the state’s Democratic Attorney General Andy Beshear — that is seen as a curtain raiser to McConnell’s own 2020 campaign for a seventh Senate term. And the Senate majority leader has been...