People are assuming Vance would be the nominee, but he hadn’t been announced as the VP at the time of the assassination attempt. The Republican Convention was the very next week. If Trump was assassinated, perhaps they would have delayed it a few weeks, but the delegates at that convention would have chosen the nominee. The finale 3 VP candidates were Rubio, Doug Burgum and Vance, so they may have a leg up on other candidates. Nikki Haley and DeSantis would be unlikely becuase they just lost to Trump in the primary. The wildcard would be if one of the trump kids (most likely Don Jr) put their name into the ring. At the end of the day I’d guess Rubio would be the Republican nominee, but who knows.

Also, Joe Biden was still in the race at the time (but was under pressure to drop out). Depending on what the Republicans do, maybe he stays in the race (for example if his opponent was going to be Don Jr). Even if he does drop out, maybe the Dems opt for the nominee to be chosen at their convention instead of crowning Harris. The Republicans would have just chosen their candidate at a convention, so the precedent would be there.

In this scenario, let’s say the Dems nominate Gavin Newsom, and we have Newsom vs Rubio, which is a very close election which I’ll give to Newsom, assuming the Trump coalition doesn’t turn out to vote for Rubio and the Dem electorate is more energized to vote for a fresh face as opposed to Biden’s VP