SCOTUS might invoke the 2020 Rule: first deny standing, later declare it to be too late to file.
Only if SCOTUS follows the Constitution...and that's a BIG "IF".
The far left base would love it for this very reason.
I'll participate in a little speculation, just for now.
If they can slide harris aside and replace her with Curious George (obama) as the VP running mate. They continue the brandon campaign and win, brandon resigns, curious george becomes president again. They could even run promoting this idea. curious george is already appearing very front and center in campaign adds. As a consolation they could promise harris the VP slot after brandon leaves. All slight of hand and all perfectly legal but probably nobody would have ever expected such subterfuge. The idea also eliminates the sticky problem of transfer of the $240 million in campaign funds dedicated to brandon.
The precedent allowing this is already set to a degree but slightly reversed. Nothing prohibits a VP from finishing the term of an incapacitated or removed president and then running on his own for two more terms. Theodore Roosevelt has already done this. The only thing now prevented is to run for office more than twice. Nothing but the voters could prevent anyone from playing this scam multiple times so long as the VP candidate was willing to risk his being raised to the throne. There was never any doubt or question that Johnson could have done it, Truman could have done it and Ford would have if he could. None of these three could accomplish either election or reelection though.
If the dims did this brandon would defeat Trump, I have little doubt. curious george would love it. You can bet this has already been proposed and even underway. curious george has already been the behind the scenes president for the last three plus years. He even said in an interview that if he could remain behind the scenes and pull the levers of the presidency he would do it. He probably has already. Consider how he has behaved on the stage with brandon lately.
As for approval of a running mate, Congress has nothing to do with it. As for approval of a successor President in the event of death, resignation or removal, same thing. The elected VP becomes President.