There are cycles in American politics. US cycles are even more pronounced because we Americans have a totally entrepreneurial presidential system. We don't have parliamentary opposition parties with a shadow prime minister and shadow cabinets. Every four years, the opposition reinvents itself.
Walking back from the convention site I chatted with a normal Bostonian for several blocks -- who must have identified me through our covert system of signals. He was mostly bemused by the Democrats' primetime speakers and told me he used to be an independent, but for the last 20 years found himself voting mostly Republican. Then he corrected himself and said he votes for the American.