1. I do not know of any legal or constitutional way to decertify a presidential election, there would have to be something in a state constitution that allows for that contingency. IOW, there has to be some law that a judge can point to and say I have the authority and the jurisdiction to make a decision one way or another in this matter, otherwise it's judicial activism. I do not believe such a law exists anywhere in any state Constitution. If there is, I'd love to learn about it. And the US Constitution leaves the matters of elections to the states, so on what basis would the US Supreme Court make any ruling to decertify a presidential election outcome?
Here's the thing: there are already existing ways to remove a president. I do not believe any federal judge will take it upon himself to rule for a decertification, or if a state Supreme Court will do so. And nor should they IMHO. I say that as one who voted for Trump in 2016 and again in 2020, and I do not for a moment like Joe Biden. BUT - so far as I know, no judge has ever ruled that Trump should have won a specific state after reviewing the evidence provided. I don't think it's going to happen folks. Maybe the election was stolen and Trump should've been re-elected. But until such time as a federal judge says otherwise and the Supreme Court agrees, Joe Biden is the POTUS and DJT isn't.
2. Now - about the part concerning the destruction of the democratic party. It's funny that the democrats are howling like crazy these days about 'the threat to our democracy' in their quest to pass certain voting/election laws, cuz IMHO it is the Democratic Party itself that is the greatest threat. I suspect they're going to get a good ass-kicking in the mid-terms, and rightly so. But don't be counting these people out, cuz they are totally committed to their agenda and they ain't gonna go away. And a part of the problem is that a whole lot of young people don't like our gov't and capitalism, even though they don't really know squat about the alternatives, so don't be counting any chickens. I recall there was talk of the end of the democratic party when Reagan was the prez, and look at them now. They own the WH, the Senate, and the House, albeit with extremely thin margins.