Let me try out an analogy: Physicists know what the coldest possible temperature is. It's about -273.15ÂșC. In degrees Kelvin, it is 0. Maybe you've heard this called absolute zero. We can't cool anything down to this temperature. We can get really close, but can't hit it. Why? https://twitter.com/NikkiHaley/status/1327305628419837955
It takes effort to cool things down. Your freezer has to be plugged in to work. The colder things get, the more work it requires to get even colder. As you get close to absolute zero, it gets really hard to get any colder and eventually you have to do infinite work to hit 0.
I think fighting election fraud is kind of like this. We can try harder and harder to eliminate it, but we can almost certainly never literally get it to zero. Like most crimes, zero is maybe a symbolic goal, but not really a practical one.
Good news is election fraud is very rare. It's rare enough that is doesn't seem to meaningfully affect races. Given the size of our nation, it might well already be about as close to zero as we reasonably can get it. It seems like our election laws mostly work.
What about trying to get closer to zero? It's hard to do that without also making it harder for honest people vote. We seem to be at a point of diminishing returns. We end up sacrificing legit votes to *maybe* prevent a few fraudulent ones, which seems inefficient.
As for mail-in ballots, there are already states that have been doing that for a while without incident. Republican and Democratic states. It seems like if a state is willing to put the effort into doing mail-in votes, they certainly can do so securely and successfully.