Perhaps no other president has so often borne the epithet of imbecile as John Tyler, who was expelled from his own party by a rump Whig congressional caucus. The vicious political infighting that characterized his term may account for the low regard in which his presidency has been held by historians, who have generally ranked him as one of the least successful chief executives, despite achievements such as the Webster-Ashburton treaty, which heraided improved relations with Great Britain, and the annexation of Texas, which added millions of acres to the national domain. Why did John Tyler pursue what appears to have been a politically self-destructive course with regard to both his first party, the Democrats, and his later political alliance, the Whigs? Was it on the grounds of principle, as he asserted? And if so, what principles? Dan Monroe has set out to explain the beliefs that commanded such overwhelming fealty from Tyler that they led to his resigning his Senate seat and exercising politically suicidal presidential vetoes. Monroe traces the origins of Tyler’s political philosophy in his early years in the Virginia legislature and the U.S. House of Representatives before ex