It probably wasn't intentional, but... Have a second look at this:

Republicans gain more voters when people are prosperous, well-fed, contented, confident in the future, independent, and feel that they have wealth and property to protect and leave to their children. Democrats gain more voters when people are in poverty, angry, envious, dependent, fearful of the future, and feel like they have been cheated by life and will never get anywhere. Oversimplistic--I am not saying all voters fall into these categories--but largely true. Think about it a while.

Well, I did - and I found an all-too-easy inference, which I can cobble together from snippets of the above, with some additions:

[W]hen people are in poverty, angry, envious, dependent, fearful of the future, and feel like they have been cheated by life and will never get anywhere, Democrats gain more voters, and control of the White House and/or Congress; thereafter, people are prosperous, well-fed, contented, confident in the future, independent, and feel that they have wealth and property to protect and leave to their children. Under those conditions, Republicans gain more voters, and control of the White House and/or Congress; thereafter, people are in poverty, angry, envious, dependent, fearful of the future, and feel like they have been cheated by life and will never get anywhere.

Cause and effect. (...and you said you didn't give credence to cyclical political theories...)

In my entire adult life, I have always been less-well off, more often unemployed (and for longer), and more fearful of misguided foreign policy and its dangerous consequences during Republican administrations than during Democratic ones. Perhaps I'm unique in this respect - I doubt it. Oversimplistic, perhaps, but solidly grounded in personal observation.