alt Hacker NewsFamously, there have been significant issues in the past (see Tammany Hall) but I don’t think it’s anywhere near as widespread as it used to be, and especially not at the national election level. I’m sure that there’s shady stuff happening in local (county) level elections, but that’s of significantly less importance to the rest of the general public
An added point about Tammany Hall is that for much of time it was a relevant political power, the US did not have secret ballots. Arguably, it was the lack of anonymity/secrecy in voting that allowed for the types of election fraud that Tammany Hall and others were known for.
The secret ballot perhaps made a particular type of election fraud, the kind done by dedicated partisans voting multiple times themselves, theoretically easier. But it removed the mechanics that allowed far more prevalent and lucrative election fraud. In the Tammany Hall era, you could buy votes and know that your paid voters actually voted the way you wanted. You could promise that your preferred candidates, if elected, would give rewards only to people who voted for them, and actually follow through with that promise. You could physically prevent people from voting with ballots that weren't yours, rather than trying to rely on demographics.