There are two particular Senate races from 2016 that I would use as an example here. There were probably dozens of House races across the country with a similar dynamic at work.
I'm sure there will be political science textbooks written about the Rob Portman (Ohio) and Pat Toomey (Pennsylvania) Senate victories last year. Both of these were Republican seats that were targeted by Democrats to help them win control of the Senate, and in Toomey's case it was a Senate seat in a state where a Republican presidential candidate hadn't won in almost three decades.
Both of these candidates faced a similar dilemma. They could publicly condemn Trump and alienate their Republican base, or they could endorse Trump and alienate moderates and suburban women. Both of these guys took a third option instead: they basically ignored Trump completely. Toomey's win was just as remarkable as Trump's victory in Pennsylvania. Both of them won very tight races, but they did not win with the same voters. Trump lost in most of the suburban areas but more than made up for that with working-class Democrats who voted for Toomey's Democratic opponent. Toomey held the GOP base in the suburbs, which was critical to his victory because he didn't run as strong as Trump among those working-class Democrats.
Ryan is a lying weasel but unfortunately he’s not going anywhere.
I thought you made some very good points, but just to keep it absolutely simple, your leading words said everything.....
“If he perceived that a loose cannon like Trump at the top of the ticket...”
Trump can’t trust anyone with that perception. Pyrrhic victory for Ryan...it’s time.