IIRC, there was a demand for administrative action put to the FEC, and this same result was announced by them way back when (Sept/Oct?).
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The “state by state” provision has to do with ballot access. Voters vote for electors, state by state, and electors are “party” entities.
Correct, and the parties choose the candidates unless one runs as an Independent. Regardless, the qualifications are determined by the Constitution and until now it was assumed that no one ineligible would run. The opposition and the media were expected to assure this. This time it failed primarily because of the media and the fear o it.
A challenge in court seems the only remedy and finding a court that will hear it, and give it a fair hearing, is exceedingly rare.