Well, consider: You're a Senate Republican. Obama nominates a guy who is certainly no Scalia but legitimately isn't the worst. You can hold out and hope that a Republican gets elected, but there's a good chance that'll be Donald Trump, and what kind of a judge is that weirdo going to nominate? You hate that guy and think he's a blemish to the name of the Republican party. Also, there's still a real risk Hilary/Sanders will win instead. AND you can expect to face more than half the media harassing you over any delay. In fact, the harassment has already begun today, Feb 13.
So a real compromise candidate might be possible. It'd likely depend on Obama and the senate Democrats as well, though.
it's actually pretty unlikely. Fivethirtyeight has a bunch of good articles about this, but the simplest piece of information pointing to it: Trump is intensely disliked by about 60% of the voting public. He's got a vocal and enthusiastic following, but once you go outside that bubble, he simply doesn't have room to grow.
I voted for Bush twice, McCain, and Romney, and I'll vote for either Hillary or Bernie (two candidates I can't stand) over Trump, and I'm far from alone.
Trump said he'd nominate his sister. I doubt he'll get the nod, and I doubt we'll see anything until after the election since it will energize both sides. It's too good a fund raising tool for red and blue to pass up.
So a real compromise candidate might be possible. It'd likely depend on Obama and the senate Democrats as well, though.