The only way it plays out with impeachment is if a few marginal GOP senators see a poll saying they'll benefit from looking bipartisan and impeaching. That's all that matters to them.
If Ted Cruz or Marco Rubio starts exploring a presidential campaign you can know that the roaches are abandoning the ship.
No Republican politician is going to vote against Trump and still have countrywide support to be his successor.
There’s also no chance that a Republican could gain more votes than they would lose by voting for Trump’s impeachment.
If they’re targeting any Republican impeachment votes it has to be the retiring senators who would like to see the party move back towards centre from the far right.