The countervailing force against all of that is tradition, the weight of history and just how much a senator's past statements actually matter.
Why? Because, according to McConnell, Obama was on his way out of office -- term-limited at the end of 2016 -- and that ruled out the Senate considering the pick.
"Of course the American people should have a say in the court's direction," McConnell said at the time. "It is a president's constitutional right to nominate a Supreme Court justice, and it is the Senate's constitutional right to act as a check on the president and withhold its consent."
McConnell was far from the only Republican to speak out in favor of waiting until after the election to consider any Supreme Court nominee.
The record then is quite clear. Senate Republicans -- from McConnell on down -- opposed even holding hearings for Garland because the vacancy came in an election year. So now, with just 46 days left before the November election -- and with Trump trailing former Vice President Joe Biden by mid- to upper single digits in most national polling, what's changed, exactly?
And so, Senate Republicans are faced with a choice between an unstoppable force (Trump's insistence that he will fill the vacancy and McConnell's promise of a floor vote for whoever he picks) and an immoveable object (their well-documented opposition to just such a scenario back in 2016).
In a way, that Trump's first term ends with the highest of high-profile tests of whether Senate Republicans are loyal to him or to their past stated principles is incredibly fitting. Ever since Trump conducted a hostile takeover of the Republican Party during the 2016 primary campaign, elected GOP officials have been content to go along with his remaking of their party (and of politics more generally) under the belief that as long as they got things they wanted in the deal -- tax cuts, more conservative judges on the federal bench -- it would be worth it.
Time and time again, as Trump has bent -- and broken -- the bounds of normal presidential behavior, Senate Republicans have, largely, stood behind him or remained mum. Sure, there's the occasional tsk-tsking or "Well, that's not the way I would have done it" quote, but, generally speaking, any resistance to Trump within the GOP has been pulverized by the fear of political reprisal from a President who demands total fealty.
If McConnell cannot muster the votes he needs to confirm Trump's pick prior to the November election, it's possible he would bring the Senate back in a lame-duck session after the election in hopes of gaining a few more votes. The theory of such a move would be that endangered GOP senators who had either won or lost in November would be freer to cast votes without fear of political reprisal. (Note in McConnell's statement that he didn't say the Senate would vote on Trump's pick before the election; he just said the Senate would vote on the pick.)
The move by McConnell in the hours following GInsburg's death sets a very clear choice for the other 52 Republican senators: Either you are with Trump and McConnell or you are against them. If past is prologue, that will be a tough duo for most Senate Republicans to oppose.