The beauty of this case is that it has little to do with Biden and nothing about fraud. It is also why so many states are signing on. SCOTUS cannot dodge this case (however they may wish to) and the facts of the case are almost guaranteed to deliver a verdict for the plaintiff. There is no question equal protection was violated as was the process of election rulemaking. The real question is what to do about it?
SCOTUS would not decide an actual election but the remedy requested is to let the 4 state legislative (elected) bodies choose new electors. This has some precedent and so it is possible that SCOTUS could provide that relief - but they might do something else instead. Even if you do have that, will the GOP legislatures get electors who vote for Trump? It will be popcorn time indeed.
Bottom line, however, is that SCOTUS can rule on a very narrow pathway, that accuses no one of fraud, decides no winner itself - and deliver a path for Trump to win 2020. Not "overturn" the election, mind you - in spite of MSNBC's breathless statements, no one has yet won the election...not till the electoral college meets and all the procedures are followed. That is why I think Roberts can safely vote on this because with the narrow ruling, essentially an important technicality, he is unlikely to be the 5th or dividing vote and it can be 6-3 giving him the cover he needs to still attend all those DC parties in the future.