As the political participation of disaffected, unrepresented voters drops, this reserve army of the unallied gets bigger. It’s especially potent in primaries, which are very low turnout events. My suspicion is that if disaffected voters could be reliably re-engaged, the parties would likely find wedge issues to divvy them up over a relatively short set of elections. But they may well divvy them up differently than the parties had previously done. This would be the seed of a realignment.