Well, that Presidential election was "mostly" clean, or rather, the actual winner, won. I've not really looked into the Congressional elections or state level elections but I'd lean on the side of shadiness occurring in them. Spielberg's "Lincoln" fictionalizes an alleged disputed election in PA (can't find documentation to verify the details, either way it's a great movie scene).

Most of the so-called "secession votes" weren't even done by the state legislatures let alone the people of the state. I think TN was a rare exception. Granted, how reliable are those turnout numbers? Say you're a Unionist in TN... just think how much intimidation occurred to get you to stay home or vote for ̶s̶e̶c̶e̶s̶s̶i̶o̶n̶ rebellion (no imagine if you're a free black, or a slave... not like they got much say in the matter!). And none of it really matters much, because an illegitimate vote is nonetheless, illegitimate. The US Constitution outlines the process for legal secession within the United States. Loyal Virginians followed that process to cut ties with rebellious Virginians, thus creating the state of West Virginia. Majorities don't make right, rather as Lincoln so correctly put it "right makes might." The reason why there's no "secession" mechanism in the Constitution for an entire state to "leave" the Union, is because that was never envisioned to be a possibility. The states entered into a compact, yes, but that was to form a perpetual Union. Calhoun's theory of unilateral withdrawal was ahistorical. Webster, Fremont, Lincoln and plenty others destroyed it in debate. The rebels simply had no Constitutional justification. They simply made it up. They didn't like that they were losing the game, complained that the rules weren't being followed (even though they were, and ironically it was the slaver rebels actually committing crimes), and when they couldn't get an umpire in that would cheat for them, they threw a tantrum and tried to quit the game. They could have made a general natural rights argument a la Declaration of Independence, but they didn't. Keep in mind that the DOI acknowledges said natural right justification to sever political ties, BUT the Founders (specifically Adams and Wilson) made stronger political claims e.g. that it was Parliament and eventually the King who violated English Law and granted the Americans independence by treating them as a foreign power, thus abdicating their authority in the Colonies.