Indeed, the Constitution * expressly * grants the authority to administer the time, place and type of voting (in the original text, “chusieren”). Federal offices in the legislations of the individual states. It also gives power to override their decisions vis-à-vis Congress. Governors, courts and any body not expressly mandated by a state’s legislature or whose authority has been delegated to it are totally inadmissible if it comes to changing the process in any way.
While it may or may not be a good idea to increase the number of polling stations (a separate discussion), a governor is clearly prohibited from explaining and setting up just because he wants to. It is also invalid for a sate-level court to restrict or strengthen any type of proceeding unless the present case objects to compliance (or lack of) with state electoral law duly enacted and in effect at the time of the election. and their decision creates such compliance. That, too, is the legitimate role of the federal courts. You can’t get into an argument and find that a state has to * xyz * or that they * don’t * have to do abc, unless those orders compel a state to obey its own then-ruling rules.
Such judicial interjections are the main concern, particularly in Pennsylvania, according to Republicans. Democrats tend to dismiss these concerns for the sake of emotion or “fairness” instead of viewing them as constitutional in my opinion, IMHO.