You are citing studies. I am citing court cases with actual voter fraud convictions. You say NO VOTER FRAUD in caps and I say North Carolina Ninth Congressional District 2018 election in which a Congressional election was overturned due to the voter fraud hat you say does not exist. Somehow you chose to ignore that case of voter fraud. Here is a data base of voter fraud cases.
There are literally hundreds of cases. Some are minor, some are major, but there's more than a few.
But even if there weren't such an overwhelming number of such cases in which cheaters got caught, you can't prove the number of cases in which people get caught isn't the tip of the iceberg of a larger number of cases in which the cheaters escaped undetected.
It is so easy to cheat. When they mailed out ballots, I went down the block and collected as many as I could. I filled them all out for Trump and dropped them in the mailbox. No body on the block was expecting them and nobody noticed they had not arrived. Sure the signatures won't match, but they'll still let half of them through anyway. My biggest haul was from the senior center where half the residents are not as aware as they used to be. Preferential harvesting is also not too difficult. You go up to the door with a Biden hat and campaign literature and offer to deliver a mail-in ballot as a service and save the voter a trip to the mail box. Then you take the signed ballot, steam it open, and evaluate if you can wash or erase the voter's mark. Failing that, you can scan it and fix the vote in two minutes on the computer and print out a "corrected" ballot. Or you can just shred it if you are really lazy. The chances of getting caught are near zero. This is so much easier than rounding up volunteers at the bars and giving them the names of dead people or even people who hadn't voted so far that day. You slip them $20 in street money and walk them to the polls. Did any of your researchers get a seat in the back room with Major Daley in the 1960 election or study the operations of city machines that ran well-organized vote-rigging operations?
We've always had dirty elections and people are incredibly naive to think otherwise. But we should realize unsolicited mass mailing of ballots will open the door to a higher level of cheating. Sending an unsolicited ballot to every one on a registration list will literally include sending ballots to dead people and people who moved away years ago, and you assert with absolute confidence none those ballots will somehow wend their way back. My position is that sending live ballots out to dead people puts the integrity of our elections at risk. You say there is no risk. I guess we disagree.