In less insane times, the death of an elderly Supreme Court justice would lead to the president nominating a qualified justice and the Senate likely confirming that figure in a few months or less. But the idea of that happening following the death of Justice Antonin Scalia sounds absolutely preposterous, and it’s going to have profound effects on both presidential and congressional elections this fall.

Let’s first stipulate that the chances of this Republican Senate confirming a Supreme Court appointment of President Obama’s in an election year are … well, Sen. Mike Lee’s own spokesman puts them at “less than zero.” I would put it at, say, 0 to 5 percent. Some would argue that stonewalling a president’s Supreme Court nominee for 11 months as a pure political play would set a horrific precedent. I would agree. And?

The most generous scenario would be that Obama appoints a judge whose confirmation easily sailed through the Senate on a bipartisan basis when appointed to a lower court. Senate Majority Leader Mitch McConnell, trying to look fair, calls that person up for a vote (assuming the appointee even gets out of the Senate Judiciary Committee). Other Republican senators filibuster. (Remember that then–Majority Leader Harry Reid’s 2014 “nuclear option” eliminating the filibuster on judicial appointments did not apply to Supreme Court appointments.) The Democratic caucus has 46 votes. Some Republicans in blue or purple states up for re-election vote with Democrats if they like, but it won’t be enough to get to 60. Republicans then argue that it’s too late in the calendar under the Thurmond rule—which is more like a guideline—to nominate a new candidate. Democrats beat Republicans over the head as being obstructionist, and the next president selects the court’s ninth justice.

… Or McConnell never even bothers to go through the motions.

So how does this affect the campaign itself?

Scalia’s death should result in an extraordinary amount of money being spent in Senate races to determine the chamber’s control. But it’s not like these races were going to be conducted on the cheap previously. Also, it’s not clear that control of the chamber is the central problem here. Senate leaders might be able to get away with blocking a SCOTUS pick for 11 months; four years is a whole different order. Senate control will affect the gradient of ideology that the next president is allowed to get away with. That’s not nothing. But it’s not the whole ballgame.

Does this stonewalling help Democrats in November? Republicans blocking a Supreme Court nomination would allow Democrats to portray Republicans as unreasonably obstructionist, though Republicans tend to take that as a badge of honor. It could boost Democratic turnout, since they have the opportunity to retake the Supreme Court for the first time in decades, if only they vote. The counter to this is that Republicans will instruct their voters to stop Democrats from forming the first liberal Supreme Court majority in decades. If early primary voting numbers are any indication, Republicans already have the advantage in prospective enthusiasm and will use the fear of a liberal Armageddon to maintain that.

As we’re all aware, though, there’s a long way to go until the general election. This turn of events would seem to rocket “electability” to the top of primary voters’ concerns in selecting their candidates. Hillary Clinton has been dangling the Supreme Court nominations card front and center already. We can now reasonably assume that it will comprise 99 percent of what she says for as long as she faces primary competition. I would like to say that the court vacancy would make GOP primary voters second-guess their support for either Donald Trump or Sen. Ted Cruz, but nothing makes GOP primary voters second-guess their support for Trump or Cruz.

If the ideological tilting of the Supreme Court is to be determined by the next president, as it seems it will, then this will be an election of monumental importance. Expect its ugliness to match.

See more of Slate’s coverage of Antonin Scalia and the 2016 campaign.