Manchin is a sure yes. He wants to be re-elected and he’s only reflecting his constituents’ views.
If Mancin votes yes especially if Collins votes no then Mancin might as well announce he is switching parties when he votes. He will be a pariah in the Democratic party.
This might be the pivotal moment where Manchin jumps across the aisle and becomes a Republican.
I thought the same about Heidi Heitkamp, so her stated decision to vote "No" on Kavanaugh probably means she isn't all that interested in being re-elected.