John Tyler, though a Jeffersonian Republican and ardent Democrat, became the second Whig President after William Henry Harrison's death.
Upon the death of William Henry Harrison in 1841, America found herself in an altogether novel situation which she had been fortunate enough not to have to face before. Never had a sitting President died in office, and never had the constitutional line of succession been forced into practice.
Now, only a month into Harrison's term, John Tyler found himself thrust into the spotlight, facing an incredibly important question: What is the purpose of a Vice President?
While many in Washington viewed the position of Vice President as sort of a "placeholder" position - having no real power but to sit in the President's seat upon his death while awaiting the arrival of a new President, Tyler set an incredibly important President by entirely ignoring this line of reasoning.
To Tyler, upon a President's death the Vice President should be given all powers, commands, priviledges and duties of a sitting President for the remainder of the current term. He had himself immediately sworn in as President and governing quickly, much to the derision of his critics.
Thus, the precedent for the Presidential line of succession was set - one of Tyler's most important accomplishments.
The politics of John Tyler were filled with important contradictions which undermined his Presidency from the very start.
He had been raised a Jeffersonian Republican (his father, John Tyler the elder had been a fervent states-rights advocate and opposer of the constitution) in Virginia and was a strong supporter of the War of 1812 under President Madison, soon after which he was elected to congress.
As a southern, slave-owning planter, however, Tyler despised the "American System" of nationalization, internal improvement and high tariffs proposed by James Monroe and John Quincy Adams.
He also opposed the Missouri comprimise which effectively split the nation into two distinct regions - the southern, slave holding region and the northern, free soil region. Tyler favored legalizing the institution of slavery throughout the nation.
His status as a Whig came not from his particular policies (which were generally in opposition to the Whig policies), but because of his personal dislike and distrust of Andrew Jackson. He supported John Quincy Adams in the 1824 election, even though he disapproved of his nationalistic policies.
In 1828 Tyler begrudgingly supported Jackson in order to vote against Adams for a second term, though he found that he despised Jackson even more (even though he supported certain individual policies, such as the opposition to the Bank of the United States, which he mistakenly believed was a demonstration that Jackson was a states-rights advocate).
John Tyler's greatest split from the "Jacksonian" camp came in the event of the nullification crisis, as Jackson was threatening force against South Carolina for refusing to submit to the federal tariff. Tyler publically denounced Jackson in a fiery speech and became the only member of congress to vote against the use of force.
The Whigs first nominated John Tyler for the Vice Presidency in the election of 1836, placing him in the secondary position in two of the three national campaigns run by the party that year (which they lost to Martin Van Buren, partly as a result of this split ticket).
Four years later, Tyler found himself nominated again thanks to his opposition to Jackson (and with little to no concern regarding his personal politics), this time under the sole Whig candidate, William Henry Harrison, the "Hero of Tippacanoe."
Their famous slogan, "Tippacanoe and Tyler Too," along with a misleading view that the candidates were more like the common citizens than their elitest opponent, helped send them to the White House in a landslide victory.
William Henry Harrison was inaugurated, and thirty-one days later, Tyler was President - but surely not the President the Whigs had hoped.
To continue the story of John Tyler, please see: The Presidency of John Tyler.
References:
"John Tyler." American Presidents: An Online Reference Resource.
"John Tyler." The White House.