Since the end of the Cold War, we have had, for the first time since the 1820s, three back-to-back eight-year presidencies. (I call it, with a nod to that earlier period, “the era of bad feelings.”) In each case, the president was someone running for president for the first time. In each case, he was elected with at least nominal majorities in the House and Senate. In each case, those majorities were gone by his seventh year and he was succeeded by a government under the unified control of the other party.
Make of it what you will.