> Separately from any constitutional challenges at the federal level, I bet many state supreme courts will be faced with challenges based on the premise that the state legislatures reached beyond their state granted powers.

I'm pretty sure that in the cases around the 2000 Presidential election (and possibly previously) one of the key federal rulings is that because selection of Presidential electors is a power of state legislatures (not states as a whole) specifically granted by the federal Constitution, State Constitutions cannot trump the federal Constitution in how that authority is allocated.