There is a way to prove that enough ballots were improperly vetted that could have altered the outcome of the election.
Every fraudulent ballot dropped can be matched to a registered voter.
What has not been done is to match envelope signatures (envelopes were supposed to be retained for just such an audit) with those signatures on file. This has been done only on a very limited basis, and consistently 3-4% were found to not even be close to a match.
Are you going to ask voters if and how they voted? Well, that is illegal.
It is not illegal, but it wouldn't prove anything since you don't have any way to line up a specific ballot to a specific voter. But what you can do is ask voters if they cast a mail-in vote, and reconcile that with the mail-in votes received. Again, this has not been done on a large scale, but where it has been done the discrepancies are about 3-4% say they didn't vote yet a ballot was cast in their name.
The system of fraud being used cannot be easily revealed unless you catch people in the act of dropping ballots into boxes.
Even catching people in the act of stuffing drop boxes will not reveal fraud. You would have to seize the ballots and get a court order to open them, and then confirm with each registered voter that they did indeed fill out that ballot and give it to the "mule." A lot of investigation to occur only days from an election.
Even then, Democrats will claim that this is OK.
In some states such as California, it is perfectly legal for one person to collect ballots from voters and deliver them to a drop box. In other states, only relatives are allowed to do so. But in no state is it legal to pay someone to collect ballots and deliver them to a drop box.
What Trump and everyone needs to do is eliminate the source of the fraud....vote by mail as well as scrub all voter registration rolls.
Scrub the election rolls, absolutely. But no court will allow the disenfranchisement of those unable to go to a polling place. There MUST be a means for absentee voting.
My proposal is to forfeit the right to a secret ballot if you choose to vote by absentee ballot and cannot turn it into the clerk's office where ID can be checked. If you insist on using either a drop box or mail to return your ballot, then the ballot inside will be tied to an individual voter by a serial number code that can only be accessed by authorized election personnel.
Then if the eligibility of a specific mail-in ballot is successfully challenged, its votes can be subtracted from the overall tally.
That is the exact point that should have been made versus the absolutist aim that the election was actually stolen. Saying that the election was not trustworthy is going to be a heck of a lot more palatable to voters than telling him that it was actually stolen, which is the moment at at which a lot of voters tune you out.