I'll go out on a limb and say there will not be a mass shooting at a polling place this year.
I believe what I might be trying to say is, in 2016 nobody (except me and a few others) saw Trump coming. As far as vast majority of people were concerned, he was the charming "you're fired" guy on TV. People like celebrities, so much so that they'll vote for celebrities just for the entertainment factor. Eight years later we have a very different landscape. Everyone knows exactly what Trump is, and practically nobody is being accused of engaging in Alarmist Non-sense for expressing fears that he will usher in a minority-rule fascist state that will do away with elections once he and his coalition of neo-Nazis and christofascists are in power.
I was eight years too early when I said that a Trump nomination would be a gift to the Democrats, and that people would be lining up at their polling places starting at one in the morning to make sure they don't lose the opportunity to vote against him. That wasn't going to happen in 2016; that's definitely going to happen in 2024. No one is apathetic about this election except the far fringes of the aggressively ignorant. It's true that Trump has his base and will still draw 70-ish million votes. But it's also true that the other side is way, way, way more motivated than ever to make sure their vote against Trump is counted, especially now that it is also a vote for Kamala. Assuming she doesn't shoot herself in the **** sometime in the next eleven weeks, she might win the national vote by eight figures, which no rigged Electoral College could overcome. I think it's more likely Trump dies or is incapacitated in the meantime than it is he simply beats Kamala Harris in a free-and-fair election at the ballot box.
To your point, the biggest threat is that one of the blizzard of post-election lawsuits makes a beeline to the Supreme Court and they vote 5-4 to overturn the results and put Trump in the White House. If they do, though, that will be the literal end of democracy in this iteration of the United States, millions will take to the streets, the blood will flow, and I definitely do not mean leftists killing red hats, because that's not how it's going to happen since leftists aren't the ones with the guns.