See, there are always two kinds of errors. In the case of voting, one kind is where you let someone vote who shouldn't, and the other is where you don't let someone vote who should. And when you try to decrease one, you increase the other, because you don't have a perfect system.
So, how much suppression of legitimate voters should we accept in order to decrease voter fraud? I think the answer should be "no more voters should be suppressed than there are fraudulent votes cast, and preferably fewer".
Well, how many fraudulent votes are cast? There is little evidence that it's a large problem. In the absence of such evidence, I do not thing that there should be large changes to try to eliminate the fraudulent votes that exist, because they are likely to cause more problems the other direction.
Note well: I do not approve of fraudulent votes. But even more I disapprove of creating a large problem to fix a small one.
But to the point of even 400 non-eligible voters participating, that is 400 too much.
If find the framing of your question bordering on disingenuous but I'll charitably assume that it is willfully ignorant.
We should have zero voter fraud. We should have zero electoral fraud.
Voter fraud itself is incredibly rare in US elections:
https://www.brennancenter.org/topics/voting-elections/vote-s...
But you position yourself as expecting fair elections, and if you really do, you would understand that fair comprises not just keeping ineligible voters from doing so, but also allowing eligible voters to do so.
There's been an incredible amount of fuckery by the GOP to disenfranchise citizens of their rights to vote. But do you care about that?
Do you care that Trump is working to install loyalists into positions of election officials who are loyal to him, rather than the historical position of neutral officials who honor the democratic process?
https://nlihc.org/resource/history-voter-suppression
https://en.wikipedia.org/wiki/Voter_suppression_in_the_Unite...
https://guides.libraries.psu.edu/historyvotersuppression/web...
There's plenty more where that came from, but I doubt you'll look at any of that because that isn't likely a concern of you.
So I ask you: is your concern about "your team" not winning or about free and fair elections. I'm pretty sure what that answer is but would welcome your response.