>>I suspect moderates (and more senior folk) in both parties will tend to threaten a nay-vote on more extreme nominees In cases where very ideological nominees

>>I suspect moderates (and more senior folk) in both parties will tend to threaten a nay-vote on more extreme nominees In cases where very ideological nominees have been presented in recent years there is no evidence that moderates have been prone to block them. So it isn't clear now what a senator could gain could gain by blocking his own parties nominee. It would require enough senators from the majority party to switch and vote against their party and maintain that united opposition against a candidate whose ideology they agree with simply because they may have qualms about how extreme his ideology is.