Alaska and Maine have a ranked-choice-voting system where you the voters rank who their first, second, third, etc. choices are. I can see where having two candidates sharing the same name can be a problem as it can confuse the voter on who is the Dan Sullivan they want. What the Democrats did here lacks integrity, but is it breaking the law? If it's not, then we may see both parties playing this game in future elections there.
Louisiana has a jungle primary where all candidates regardless of party is on the ballot. If one of them achieves 50%+ they win outright eliminating the need for them to run on the general election ballot, otherwise the top two go to the general election. That could result in both candidates being from the same party. I find problems with both.