I think if that actually happened, it would be the first time, right?
Has there been a sitting president who has delayed nominating a candidate until after an election?I'm not talking about confirmation which depends on procedure and votes in the Senate, but just a Presidential nominee.
Voluntarily? No- the whole issue here is that there was a nomination
denied, of Obama's by McConnell in 2016, on precisely the ground that McConnell is deciding is irrelevant today. Just for
one example, here's McConnell on Meet The Press, Mar 20, 2016*-
The principle involved here, Chuck, when an election is underway, as Joe Biden was talking in 1992, an election's underway, the American people are about to weigh in on who is going to be the president. And that's the person, whoever that may be, who ought to be making this appointment.
That's just about as plain a statement of principle as you can expect; and McConnell's waffling now is about as plain an example of hypocrisy as anyone should need. Bottom line is that there's no need to rush the nomination to get it done before the election- there was a whole year between the death of Scalia in 2016 and his replacement by Trump after his election, and 8 Justices are as full a Court for their decisions process as 9 would be; if Trump is re-elected, then he can go ahead and nominate without having lost anything but a little time. If, OTOH, Biden wins, but McConnell has rammed through Trump's appointee, well...surely you can see the problem?
(The reference to 1992 by McConnell is sort of interesting too. That year, we had Bush (the elder), an incumbent, running against Clinton (the...taller?)- pretty much the same situation, incumbent vs challenger, we have today. There were no SC seats up for nomination that year, but Biden's hypothetical position then was the same as McConnell's in 2016. And McConnell today is reversing that position based, in part, on the fact that Trump is an incumbent, though not (yet) a lame duck- a distinction he didn't seem to think important enough to mention for Bush's case. IOW, he's making it up as he goes along- his qualifications and hair-splitting are more out of necessity than principle.)
*Sorry, it's a transcript of an entire MTP show, so it's pretty long, and no way I can see to link directly to the McConnell quote; you'll have to scroll about 2/3 of the way down to see it.