With government this big, every election is a national election. Harry Reid is the most impactful Senator in all 50 states, period. Obama impacts all 50 states, period.
Local elections are something about 40 years past their sell by date.
My point being that there’s little that can be sprung from DC that has an impact in a state or local election.
In a presidential, you can reveal a drug bust in the past of a candidate, and that will impact the entire electorate.
You can’t tell me Thad Cochran slept with 3 gypsies and a Nazi in Mississippi, and have it impact McConnell in KY.