As this "Presidential Cycle" is fascinating for me today I've spend the whole day (too much time on my hands) to read practically everything Zee and others in 2005/6/7 had to say about it (Zee, thanks for pointing to your 2006 posts, but actually yours from 2005 are even more illuminating). It seems to come down to this:

Jim (in 2007): I believe the "presidential cycle" effect to be a crock. For my reasons, see post 185404. The bottoms in 1949-1953-1957 tend to indicate to me that a cycle exists that is a few years long, often four, but that it doesn't necessarily align with years divisible by four.

Zee (in his reply): Whether you consider the cycle to be a Presidential Cycle or just a four year cycle, there is little doubt that a cycle exists and it is approximately four years in duration.

I think the evidence (Zee, Grantham etc.) is overwhelming and that it's not "just a four year cycle", but definitely a "Presidential Cycle". Why? Because a cycle doesn't come out of thin air. It's an effect, so there must be a cause. And the only plausible argument I found why such a cycle exists (which even Jim admits, though he's not convinced about it being exactly 4 years nor about it being presidential) that makes sense is what WendyBG said (MI-178033, 11/16/2005):

http://datahelper.com/mi/search.phtml?nofool=youBe...

Again: Even Jim admits to a cycle. A cycle does not come out of nowhere, there must be causes, (psychological) reasons. WendyBG presents them. This for me is convincing, more than "Ok, there is a cycle; no idea why".

One can be of different opinions though whether Zee's follow-up work in which he tried to differentiate between months and sectors might be too extreme for one's personal taste or not, but the evidence data for the general principle is so convincing that it's extremely tempting to use this more than anything else as "primary timing indicator" (eventually in conjunction with Zee's 9 months Oct-Jul instead of Oct-May plus "Superior 8").

Of course it's not perfect. 2007/8 dramatically contradicted it: 2007 (3rd PC year) was a down year, 2008 (4th year) even a crash year. During the PC bullish period from Oct 2006 (2nd year) to the end of the cycle Nov 2008 (4th year) the S&P went down a full 35% (would be interesting how often this happened, how often the bullish around 2 year period actually was a Desaster). And during the current and the previous cycle the 1st year also contradicts it --- but the other 2x 3 years are fully (as far as one can say that yet for 2024) in line with it.