I think John Q. Adams was, too.
While John Q. Adams did serve most of a term as a Federalist Senator from 1803-1808 (he broke with the Federalists in 1808), John Q. was the last of three successive Secretaries of State (Madison, Monroe, and John Q.) to be elected President. That's why it l;ooked like it was corrupt deal when Adams named Clay as his Secretary of State because that position had become something of an heir apparent. Three other former Secretaries of State have become President, but not as sitting Secretaties. Those other three are Jefferson, Van Buren, and Buchannan.
