Which is why they are likely to put up token opposition - enough to placate their supporters. Everyone panders to the center when election time comes, because that's where most of the voters are. This is why the rhetoric is extreme during the primaries, but is significantly toned afterwards.
They have a majority of Senate. They don't need token opposition. They can just decide, as Mitch McConnell has already said, that this is a rare opportunity for the people to vote directly on the direction they want to take the court, and that's that.
This isn't unprecedented. Obama is a lame-duck President facing a majority opposition party in both Houses of Congress. His influence is close to its nadir. Scalia is a lion of the GOP. It would have been hard to replace him in 2015. It's probably impossible in 2016.
That depends on whose definition you use, but this discussion is mostly about precedent; look up the "Thurmond Rule" to see why technical strictness about the term "lame duck" isn't really an issue here.
The Thurmond Rule, which is amorphous and inconsistently applied, only applies when an incumbent has "six months or so" remaining in his term. We are still several months away from that excuse being valid.
Will the central-mass of the voting public be amused by yet another "obstructionist move" by Republicans? That is how it will be spun by the Democrats: the ads will basically write themselves ("instead of working, the GOP is shutting down government. Again")
Refusing to confirm a nominee isn't "shutting down the government", and speaking as a liberal and moreover a supporter of the Democratic coalition, I don't think our side does itself any favors by pretending like the GOP's entirely predictable refusal to allow Obama to appoint a Supreme Court justice on his way out the door is unprecedented or harmful.
The GOP is making Scalia's replacement a campaign issue. So be it! If the Democrats win, they'll have earned a mandate to replace a lion of the Republican Party with a committed liberal.
Which is why they are likely to put up token opposition - enough to placate their supporters. Everyone panders to the center when election time comes, because that's where most of the voters are. This is why the rhetoric is extreme during the primaries, but is significantly toned afterwards.