Not “change” so much as depress. I’ve no idea how valid it was, but there was a theory that the early call for Florida (for Gore) in 2000 depressed Republican voting in the western states since it seemed unlikely for Bush to win.
I’m not saying I agree, mind you. Just explaining the theory.
The problem is more one of voter turnout.
People are often motivated to vote by the President being on the ballot, but they are also voting for senators, governors, state legislators, mayors, water districts, bond measures, etc. If people decide that the President has already been elected, so there’s no reason to vote, then they’re not having input on the local issues where their vote is still relevant.
You might even be able to do it without the legislature getting involved. All you have to do is have the board of elections declare that the opposing candidate is ineligible to appear on the ballot,like they tried to do with Obama in Arizona.
It was actually the Penna. House Majority Leader who said that, and the Penna. Supreme Court doesn’t seem to think that at all.