
Tyler was the tenth President of the United States from 1841 to 1845 after briefly being the tenth vice president. He was elected as Vice-President on the Whig ticket in the 1840 election with President William Henry Harrison. Tyler became President after Harrison's death in April 1841, only a month after the start of the new administration. Tyler was a very strong supporter of states' rights. As president he supported nationalist policies only when they did not infringe on the powers of the states. His unexpected rise to the presidency clashed with the presidential ambitions of Henry Clay and other Whigs and it left him estranged from both major political parties.
Tyler was born into a prominent Virginia family. He represented his state in the US House of Representatives from 1816 to 1821. In the 1820s the nation's only political party, the Democratic-Republicans, split into factions. Tyler was initially a Democrat, but he opposed Andrew Jackson during the Nullification Crisis, seeing Jackson's actions as infringing upon states' rights. He also criticized Jackson's expansion of executive power during the Bank War. This caused Tyler to leave the Democrats and join the Whig Party. Tyler served as Governor of Virginia from 1825 to 1827 and as and a U.S. Senator from Virginia from 1827 to 1837. He was put on the 1840 presidential ticket to attract states' rights Southerners to a Whig coalition in an effort to defeat Martin Van Buren's bid for re-election.
With the death of President Harrison, Tyler became the first vice president to succeed to the presidency without election. He served as President longer than any other president not elected to the office. He acted decisively in establishing his authority as president in a time of constitutional uncertainty. Tyler immediately took the oath of office, moved into the White House, and assumed full presidential powers, creating a precedent that governed future successions. This was eventually codified in the Twenty-fifth Amendment.
Tyler did sign into law some of the Whig-controlled Congress's bills, but he offended the party leadership when he vetoed the party's bills to create a national bank and raise the tariff rates. Tyler believed that the president should set policy rather than Congress. He tried to to bypass the Whig leadership in Congress, most notably Kentucky Senator Henry Clay. Most of Tyler's Cabinet resigned early on in his term. Whigs mocked him by calling him "His Accidency". They expelled him from the party. Tyler became the first president to see his veto of legislation overridden by Congress.
Although he met considerable congressional resistance when it came to domestic policy, Tyler had several foreign-policy successes, including the Webster–Ashburton Treaty with Britain and the Treaty of Wanghia with Qing China. But it was in his dealing with the then-independent Republic of Texas that was the centerpiece of his presidency. Texas had separated from Mexico in 1836. Tyler saw its annexation as providing an economic advantage to the United States, and he worked diligently to bring about this goal. That he was able to do so without the backing of his own political party is quite impressive.
Tyler hoped to win election to a full term as president, but he failed to gain the support of either Whigs or Democrats. On learning that the Democratic candidate James K. Polk also favored annexation of Texas, Tyler withdrew his candidacy to support Polk. Polk won the election, and Tyler signed a bill to annex Texas three days before leaving office. The process was completed under Polk.
At first Tyler's retirement saw the former president disrespected by his contemporaries. But when the Civil War approached in 1861, Tyler played the role of elder statesman as he tried to broker a peace. When this was unsuccessful, he won election to the Confederate House of Representatives shortly before his death. He is the only former President to be buried with a Confederate flag draping his coffin.
Despite his political resolve in asserting his authority and creating a lasting precedent, Tyler is considered an obscure president and has little presence in American cultural memory. In The Republican Vision of John Tyler, author Dan Monroe wrote that the Tyler presidency "is generally ranked as one of the least successful". A survey of historians conducted by C-SPAN in 2017 ranked Tyler as 39th of 43 men to hold the office. But Tyler's assumption of complete presidential powers set an important precedent. His successful insistence that he was president, and not a caretaker or acting president, was a model for the succession of seven other presidents and the correctness of Tyler's action in assuming both the title of the presidency and its full powers was legally affirmed in 1967, when it was codified in the Twenty-fifth Amendment to the United States Constitution.
Professor Crapol argues that Tyler "was a stronger and more effective president than generally remembered". Tyler was a president without a party." Crapol argues that Tyler's allegiance to the Confederacy overshadows much of the good he did as president. He writes, "John Tyler's historical reputation has yet to fully recover from that tragic decision to betray his loyalty and commitment to what he had once defined as 'the first great American interest'—the preservation of the Union." His lack of success as president was due to external factors that Harrison would have had to confront. In the aftermath of Jackson's aggressive use of the powers of the Executive Branch, the Whigs wanted a president who would be dominated by Congress. Henry Clay treated Tyler as a subordinate. Tyler refused to go along with this, leading to the conflict between these two branches of government. Crapol and others argue that Tyler does not get enough credit for sticking to his principles on this.

John Tyler is a difficult subject to properly assess, as is acknowledged in the most recent biography about him entitled President Without a Party: The Life of John Tyler by Christopher Leahy (reviewed here in this community.) As the author of that book concludes, John Tyler remains a riddle in many ways. Tyler was a product of his times. He supported slavery over union likely because that's how he was raised. His intellectual struggles appear to have been rooted in ego as much as in principle. Even with Leahy's laborious effort to understand John Tyler better, his legacy leaves the 10th President as difficult to understand as ever.
Today the general public has little awareness of John Tyler at all. As Robert Seager II, the author of the 1963 book And Tyler Too: A Biography of John and Julia Gardiner Tyler put it, "His countrymen generally remember him, if they have heard of him at all, as the rhyming end of a catchy campaign slogan." In a 2014 Time Magazine article on the "Top 10 Forgettable Presidents", the writer notes: "After John Tyler earned the vice presidency on the strength of a campaign slogan that tacked him on as a postscript — 'Tippecanoe and Tyler too' — his fate as a historical footnote seemed likely; and when he ascended to the presidency following the death of William Henry Harrison, being dubbed 'His Accidency' made it a lock."