Earlier quoted context omitted.
There would seem to be precedent for this now. Justice Antonin Scalia died in February of 2016, a replacement was nominated in March of 2016, and because Scalia's seat had become vacant during an election year, the Senate would not even consider a nomination from the president [0]. [0] https://en.wikipedia.org/wiki/Merrick_Garland_Supreme_Court_...
McConnell immediately clarified his position was "the Senate shouldn't consider a nomination in an election year if it's controlled by my party and the president isn't in my party" -- no kidding, this was his actual clarification.
What happened with Garland had happened numerous times before:
> In short: There have been ten vacancies resulting in a presidential election-year or post-election nomination when the president and Senate were from opposite parties. In six of the ten cases, a nomination was made before Election Day. Only one of those, Chief Justice Melville Fuller’s nomination by Grover Cleveland in 1888, was confirmed before the election.
By contrast, if Trump doesn’t put up a nominee, it will be literally unprecedented.