As Donald Trump tightens his grip on the Republican nomination – even with Nikki Haley still in the race – politicos are ready to play their favorite quadrennial parlor game: Who will be the vice-presidential nominee?  In 2016‚ Trump’s selection of Mike Pence as his running mate was a surprise; Pence had supported Ted Cruz in that year’s nomination contest. But Pence had two assets Trump wanted: congressional experience and the ability to lock in social conservatives. This odd couple...