I see three concerns about voter "irregularities": vote fraud, obstruction at the polls, and disenfranchisement through manipulating laws and rules.
Hey, I'm from Chicago where "vote early and often" is more than a slogan, it's a career path. If you believe the mythology, this is mostly democrats. This is cheating, and it is illegal. It undermines our democracy by overrepresenting a point of view. It should be investigated and prosecuted to the fullest extent of the law. There is little evidence that this happens regularly at a large scale. The good news with this one is that everyone still has a voice; the bad news is that widespread abuse could dilute and overwhelm those voices and the process.
Obstruction and Intimidation at the Polls
This is bad. Trump's call to his followers to get out to the polls is troublesome. If they keep it under control and do not attempt to intimidate or obstruct, that's ok. I believe that there is considerable risk of mob rule, with zealots overstepping morality and the law. Nothing to see here yet, but if bad stuff goes down on Election Day, those people should be prosecuted to the fullest extent of the law. This, in my opinion, is worse than vote fraud because, if it comes to pass, it is denying people their rightful voice in the government.
Manipulating laws and rules
There is a circle of American hell reserved for these people. Recent efforts to reduce early voting, mandate specific IDs, and to manipulate voting laws and rules in order to reduce (mostly minority) participation are completely against our national values. They're doing it through, "legal means," which is code for passing laws following the proper procedures even though they will eventually be reversed. Even though these actions may not be obviously illegal, they tear the fabric of our nation by attacking access to voting. To me, this is a horrendous abuse of power, and the worst of it is that once in power they have the ability to manipulate voter outcomes and retain power through gerrymandering and institutional voter suppression.
There are plenty of people who I wish were not voting, and probably many that wish I wouldn’t. That’s all good. However, it is a fundamental principle in the United States that you have the right to vote. Efforts to deny that right or to distort the results must not be tolerated.