The document cited above makes clear that Congress assumes 'penultimate' authority with the support of the U.S. Supreme Court for this claim of authority. For this discussion we will accept the Congressional claim of authority at face value. Therefore, we conclude that the U.S. Congress is also most responsible for the inequities of American elections.
The states do whatever they wish to do because the Congress implicitly condones whatever is done at the state level until or unless the Congress choses to preempt state action. Whatever goes unchallenged at the state level is presumptively upheld by the courts whenever the Congress has refused to act specifically on that issue. Over time ample precedent is built to sustain Congressional inaction.
The partisan coalition of the Congress assures that no state action will be questioned that serves to sustain that coalition from competitive threats unless it takes a form that is grossly embarrassing to the democratic facade.
Oklahoma is a state whose political coalition seems to pride themselves in skating as closely as possible to the grossly embarrassing with its ballot access law, for example. I would like to know if there is any correlation between political corruption (by the number of officeholders convicted) in a state and the restrictiveness of that state's ballot access law. Any political science students want to take on that project?
While the Oklahoma Legislature has a despicable record on this subject since David Boren was in the State House of Representatives, the U.S. Congress claims for itself the discredit of being the most contemptible of the two institutions. In these matters, the courts know what Congressional intent is: leave well enough alone.
The same analysis holds for mere vote counting between coalition members. Either party candidate is far preferable to outsider party candidate. Since losing or stealing votes from outsider candidates does change the final outcome of the election between a D or an R, it's just a technicality. Unless you can poll more than 33 1/3 of the vote, none of your votes really matter. But elections can also be corrupt even between the members of the coalition. One one wonders how the U.S. Supreme Court really decided the 2000 election. Did they just flip a coin in chambers? Letting the people decide is a mere formality. The penultimate authority – Congress – didn't want to touch the election even though it was their constitutional responsibility to do it. Why not left the SCOTUS flip a coin and declare their decision set no precedent?
What constitution? Never mind. Nothing to see here. Move along.