Nor will I.
All I can figure out is that the smug SOB figured that he's so far ahead in the polls that he could afford to endorse Pence instead. (did he think that weaseling would appease enough voters for victory?) Keep in mind that Senator Portman got the ball rolling with gay marriage "in support of his gay son"
Trump can build a coalition with a Democratic US Senate. There only a handful of Republican US Senators worth saving.
It’s all going according the the Trump/Clinton pre-arranged plan. Divide and conquer.