FTR, I don't think there is any chance that enough Republicans will vote to convict Trump to actually convict and subsequently ban him from future office, regardless of how well the House Managers present their case, and how bumbling and ridiculous Trump's defense is. However, I thought it would be a nice thought exercise to speculate what even the impossible, 17 Republican theoretical conviction vote would look like, presuming of course that all 48 Democrats and the 2 Independents vote to convict as expected.
So the first 6 must-haves are obviously the 6 Republicans who voted that the trial itself was Constitutional.
1. Romney
2. Toomey
3. Murkowski
4. Collins
5. Sasse
6. Cassidy - I think the 5 above are a lock to convict, but thinking about it, if Cassidy is going to stand on principle, ie., "I'm following the Constitution and voting for who I think makes the best case", he's unnecessarily painted himself into a corner if he wanted to acquit Trump later... so I'm thinking he's pretty much made up his mind that he's leaning towards voting to convict.
These next ones I think are actually at least possible,
because of various factors.
7. McConnell - I think McConnell would definitely be the 17th vote if it came down to it. He's newly re-elected and unlikely to run again so he can convict with impunity. Plus he's already openly condemned Trump. I just think he's less likely to stick his neck out for no reason (cue the turtle jokes) if there isn't going to be a conviction.
8. Lee - He ratted Trump out for accidentally calling him, when trying to reach Tuberville to beg him to stall the vote, while the insurrection was in progress and Pence was being rushed off the floor as the insurgents were trying to break into the Senate floor. He wouldn't have disclosed that if he was completely loyal to Trump.
9. Graham - He is such a spineless, shameless opportunistic, self-serving, flip-flopper that I have no doubt in my mind whatsoever that he would stab Trump in the back without hesitation if he felt like that was the way the wind was blowing. So he's a possible for sure.
10. Portman - He is one of the least conservative Republican Senators, representing a purple state, and I believe he has announced he won't seek re-election, blaming the partisan gridlock. That may be a signal that he is planning to dump Trump on his way out.
11. Rubio - If Rubio wants to run for President again (he does), he needs Trump out of the way. So he may vote to convict for purely self serving reasons.
12. Scott - He is the only black Republican Senator, so he may have some misgivings about Trump leading a Motley crew of Proud Boys and other assorted white supremacists to attack the capitol. The problem is that he is up for re-election in 2022, so he has a lot of pressure on him to avoid a primary.
13. Grassley - He's 87 years old and he's been in the Senate for 40 years so I'm thinking that he's not going to seek re-election in 2022. Having served that long, Grassley may also still have some affection for quaint notions like Democratic norms and peaceful transitions of power. He may also have some sense of friendship/collegiality with Biden, having served together so long and resent Trump for denying Biden's win.
These next Senators I regard pretty much as impossible, but they are all
rated less conservative than Cassidy, who has already voted against Trump so that's at least a consideration.
14. Johnson - He's from Wisconsin as well.
15. Sullivan - He's from Alaska like Murkowski and just re-elected, so safe from any primary challenges. Also a lawyer, FWIW.
16. Thune - Facing re-election in 2022 and from South Dakota so the longest of shots, but may have Presidential aspirations (See Rubio)
17. Young - Very young and Facing re-election in Indiana in 2022, but also a college professor and a lawyer, so who knows?
18. Burr - Also a long shot, from North Carolina and facing re-election in 2022.
19. Shelby - From Alabama and facing re-election in 2022, but also a lawyer.
20. Hagerty - He's brand new to the Senate so, no voting record, but he's a newly elected in Tennessee, so possibly an arch-conservative.
Well... I must say that was... an interesting (depressing) exercise.