There is a huge issue. Even the nonsense that happened in 2000 was an equal protection issue; as counties (namely democrap ones) came up with different ideas on what a chad was, the SCOTUS ruled for it to stop.
All one would have to do is call into question any states count of the vote.
I'd argue that this is irrelevant because the purpose for the count is different, and proponents of a National Popular Vote Compact are using the state elector votes for a different purpose than intended by the Constitution. As long as the vote is proper within the state for the Constitutional purpose of selecting electors, the state's obligation is met and other states have no say in what another state does for their own usurped purpose.
My second argument would be that states are not Constitutionally required to have a popular vote to select their electors, it's just that the legislatures of the several states have chosen to do so. Just because some states have currently chosen this method does not bind them to this method forever, as the Constitution gives the states the power to select their method, and that power is not limited by time or once chosen. Therefore, a compact of other states cannot bind a state to a method, thereby removing its own right to change its method of choosing electors in the future.
Even the nonsense that happened in 2000 was an equal protection issue; as counties (namely democrap ones) came up with different ideas on what a chad was, the SCOTUS ruled for it to stop.
You are correct, but this was limited only to the count in Florida, which is what I originally said.
Perhaps I was imprecise when I said that "their vote is protected within their states when they vote for their desired slate of electors." What I meant was that the concept of equal protection applies within a state (the protection) because the whole state must vote the same way for the same slate of electors. Since different states can choose different methods of selecting electors, there is no single "equal protection" that can be applied across different methods of choosing, especially if a method can include no statewide voting at all.
In the case of Florida, the definition of a chad was only a small part of the issue. The main issue was limiting the recount only to the most densely populated Gore counties. The equal protection argument was that the voters in the other counties were not allowed a recount of their own votes as well, giving Dade/Broward/WPB an advantage. That argument was accepted 7-2 that the whole state must be recounted. The second argument was that the method of determining overvotes, undervotes intended votes(hanging chads) must also be standardized across the counties, and SCOTUS voted 5-4 that Florida did not have time to do all this within the certification window. SCOTUS stopped the recount lest Florida lose all their electoral college votes, disenfranchising all the voters in Florida over the antics of the voters in West Palm Beach, Ft. Lauderdale, and Miami.
As another example, if you have the case of Florida with hanging chads, and another state uses a pen to fill in a circle, and a third state uses touch screens, then how do you derive an "equal protection" across these states for the purpose of a recount? You can't, so equal protection must be limited to voting within each state.
-PJ