granted, our SCOTUS has always had a tendency to torture the interpretation of interstate commerce to exert federal dominance over everything, but even this would be a stretch
This is not an interstate commerce issue. The Constitution gives Congress the power to change regulations regarding voting, but that does not apply to this case:
"The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators."