The White House is a metronome in one very important way.
Since the 1928 election, the following trend has been consistent.
Parties peak, and slowly lose power until the other party takes over, and peaks and slowly loses power.
Even when one party won many elections in a row, it followed this pattern.
So Truman in 1948 won less votes then FDR in 1944, who won less votes than he did in 1940, who won less votes in 1936. Papa Bush got less votes in 1988 than Reagan did in 1984.
There can always be an exception, but it seems to be a mistake to assume that an exception is the likeliest outcome.
How can you possibly think this is logical? Seriously!?
It seems logical enough to me as a combination of several tendencies (Losing parties get more concerned about picking nominees that appeal to the center, swing voters get tired of the party in charge, Presidents concerned about reelection pick policies with short-term benefits.)
No offense, but you're not a logically thinking person as far as I can tell. But, just think of it this way, the null hypothesis is that every Presidential election is a toss-up. Each major party has about a 50% chance to win, all things being equal. You have other factors like incumbency, extrinsic events, fundraising, campaign organizing, candidate quality and such which influence each particular election. To me, that is the far, far, far more logical way to look at Presidential elections, especially when we have a tiny n size which makes your analysis basically akin to looking at goat entrails in terms of methodology.
Thus, Roosevelt only winning a minor landslide in 1940 is a regression towards the mean. It was more about the facts on the ground particular to 1936, than it was about 1940. Similarly, you have popular, charismatic people like Reagan or Bill Clinton. The fact that they won by significant margins may say more about their talents and the political situation in their election years. In 2016, the Democrat will not have the advantage of incumbency. That's the only valid point you have.
