After President Wilson's debilitating stroke in 1919,
Edith Bolling Galt Wilson effectively took over the Presidency for her husband by claiming to be able to understand what he was saying when others could not. She always claimed that she only decided what was important enough to bring to Woodrow's attention (which is a powerful position to be in all by itself), but others claim that Woodrow had lost most of his cognitive abilities and Edith's position as "interpreter of his wishes" was really a front for total control.
After stealing the election of 1876 (the first of many Republican election theft attempts, successful and otherwise), Rutherford B. Hayes complained bitterly about the debt he owed to the party bosses who pulled off the theft. He received almost daily instruction from them, was not permitted to name his own cabinet members, and was not allowed to formulate policy without the prior consent of his invisible masters.
After Vice President Martin Van Buren won the office, he inherited General Jackson's cabinet and policies. Once he began to assert his own authority and began to tone down the Jacksonian preferences for war and territorial expansion, he was effectively written off by his party and doomed to be defeated in the following election.
Edit: And then there was Reagan, who was stupid
and falling into senescence
and controlled by a criminal cabal. I believe it was his Presidency which served as the model for the Bush years, and I believe that Bush was chosen specifically
because he too is stupid in addition to being a narcissist. The larger the crimes envisioned, the dumber the figurehead President has to be to allow the crimes to occur.
Hence, Sarah Palin.