Look at the winning margins of the GOP senators. How many could withstand a 20% to 50% loss in GOP support if they voted for Trump removal? I guarantee if Trump is removed, the GOP base will be so demoralized that a significant number will sit at home - 20% to 50%. (I bet closer to 50%!). Not only would these GOP senate turncoats go down but so would down ticket - from governor to dogcatcher.
Also nothing beats the perks of being a senator (except maybe being Prez & VPrez!). No beltway job, no NGO appointment, no big industry job, no cabinet position, the power, prestige & moo-lah for your supporters Kith & kin would be gone! Unless you retiring and going to the rest home to die you aren’t going to deliberately jeopardize it! Yes there are fools that do, but in group of 55 people there are always a handful of fools!
Yes, conviction is in the senate is unlikely but if a number of Republicans turn on Trump it would give the Dems something akin to a PR victory that could damage the president. Republicans in general seem to fear media criticism and quickly collapse at the first sign of it.
I believe that some on “our side” are inclined to do that also because they resent Trump and see him as an “Outsider”. I worry about that scenario.
However, I agree with you that Republican turncoats could have a disastrous effect on the GOP at all levels. Voters would be extremely pissed off and retaliate if more than a handful sided with Democrats against the president.
That said, if the FISA report is as damaging as it is being reported to be it will make it very hard for senate Pubbies to go against Trump in spite of their inclination to do so. As you said, they love their jobs and that is of overriding importance to them. Being forced to leave and be cut off from the Swamp’s lucrative benefits is their single biggest fear. After all, they are there for themselves and not us.