Spoiler alert, contrary to the spin of the media, they are relying on evidence, and their theories are legally cogent.
The courts need to determine the claims on their merits.
Repeating this in this thread, since it is more relevant here.
Listening to this press conference.
So far as I can tell, the theory is that Biden got help from George Soros, the Clinton Foundation, Antifa and the Venezuelan government to rig the election by making cities vote for the Democratic candidate.
But they also let Republicans win Senate, Congressional and local races for... reasons.
It is a national conspiracy that they will probably file suits about in a couple of states only. Maybe. Despite it being nationally coordinated across many states they won't bring a case about that.
But they are working to "overturn the election" in a number of states. (Yes, he used the words "overturn the election" himself.)
There is a lot of evidence and only some of it is the stuff that has already been thrown out of court in other cases.
They aren't going to show this other evidence, though.
That's ok because Rudy can smell crime.
To quote Voltaire,
"Certainement qui est en droit de vous rendre absurde est en droit de vous rendre injuste."
(Usually translated as "Certainly anyone who has the power to make you believe absurdities has the power to make you commit injustices.")
