It appears you've divorced the nominating process from the general election. I see both as a continuum even though the nominating process is not not prescribed in law. And then there's Lynch's meeting with Bubba Clinton on the Arizona tarmac during which they discussed only golf and grandchildren. No rigging there, by golly! So an election might not be rigged in obvious ways that are illegal and can be proven. I still have my doubts, especially in light of Oregon's automatic voter registration system. Low information/motivated voters who can't even take the time to register even though it was already easy, now have a ballot. As you wrote, getting more people to vote appears to favor Democratic candidates so why wouldn't Kate Brown suggest as the state's attorney general, and then as the governor, sign into law a "rigged" system that favors her political party. It just goes to show that rigging an election can be done subtly and legally. The ethics, however, are questionable.