Some do think so, but there is also a material difference in needing to be intimidated at the time of the vote being cast vs any point in the future as well.
I think the bigger concern is that mail in ballots lead to fake ballots being submitted. Though I've seen no convincing evidence of this happening at any meaningful scale and the arguments seem unconvincing since you don't get a ballot unless verified with a state ID and your ballot has a unique ID associated with your name, preventing a double spend.
Personally, my concern is that with mail in ballots some nutjob that believes there's ballot stuffing can set fire to the ballotbox and even though they're caught it's a major inconvenience to get a replacement ballot and the websites that show your ballot is received take days to update.
But I still love mail in voting. My state sends a candidate brochure with it and I can take my time to actually look up all those random candidates' policies. It takes me hours to actually fill out my ballot but that's a feature, not a bug (there's nothing preventing you from along party lines but frankly I'd be happier without parties)
In 2020 a number of states were sending out mail-in ballots to every single registered voter, even if they didn't request it. Those states were CA, CO, DC, HI, NJ, NV, OR, UT, VT, and WA. [1]
And that's completely fine, because each mail-in ballot is associated with one voter, and the system is designed to make fraud very obvious and difficult to scale.
If thousands of people were told "you already voted" when they showed up, then that would be very very obvious.
They also really do look at signatures and contact voters to cure ballots if they're unsure.
Mail-in ballots tend to be counted (and received) after in person ballots, so you don't need to worry about in-person conflict. If we go the other direction (mail-in ballot rejected because the person had already voted), it was indeed in the tens of thousands. In 2024 about 584k ballots were rejected. [1] 11% of those, more than 64k, were because the person had already voted.
Not to mention that you can catch double voting across state lines. It's not common that people do this but it does happen and people are really looking for it.
Hell, the fact that so many people have been looking for massive voter fraud for about a decade now and haven't is pretty telling. People aren't good at keeping secrets and if it's being done at scale it would be uncovered or leaked. Accidents and stupid people happen, but that works both ways
People were being unknowingly registered to vote, even if they weren't eligible to vote when they would get IDs. People move. They get sent ballots. Now you have tons of ballots that aren't really valid, but they're out there and usable. It makes illegal ballot harvesting a lot easier as well if there's no active step where the ballot must be requested. I have to request my ballot every election. it takes 5 minutes, I can do it online and I assert that I'm a citizen and am eligible to vote. I can also do that by mail and I get a mailer to do so. There's no reason to not implement that safeguard.
it depends on the state and how thorough their verification system is. I can only speak for IL, but in order to request a mail in ballot, you must be registered to vote first. Even if you register online, you must at minimum provide a DL number or SSN, and the state will associate a signature with your registration. Which is then cross referenced to the signature on your ballot envelope. If you don't have a signature and you try to vote by mail, and in the slim chance your registration is actually approved, you are now a first time non signatures voter, and your mail in ballot will be provisional at best.
This is why many of the election fraud claims focused on lax signature verification of ballots as well as the lax mail in ballot address locations. I feel that IL elections are probably more secure, but only because the state is solidly one party and comically gerrymandered anyways.
But technically, yes, a ballot harvester could send ballots on your behalf if they have enough information about you.
For me the problem with mail-in votes is that they are (in many jurisdictions) allowed to come in long after the in-person voting is closed, and the preliminary results are annouced. So it creates the space for manipulations, where you count the in-person votes first, and, if the score is close, then a week after the election day half a million of mail-in votes mysteriously comes in and swings the vote one way or another.
The postmark must be on or before voting day. I cannot fathom how people have bought into this idea that they can be sent after the preliminary voting has happened.
Personally, my concern is that with mail in ballots some nutjob that believes there's ballot stuffing can set fire to the ballotbox and even though they're caught it's a major inconvenience to get a replacement ballot and the websites that show your ballot is received take days to update.
But I still love mail in voting. My state sends a candidate brochure with it and I can take my time to actually look up all those random candidates' policies. It takes me hours to actually fill out my ballot but that's a feature, not a bug (there's nothing preventing you from along party lines but frankly I'd be happier without parties)