He was the sole nominee on the 1840 Whig presidential ticket as William Henry Harrison's running mate. Under the campaign slogan "Tippecanoe and Tyler Too", the Harrison-Tyler ticket defeated incumbent president Martin Van Buren.
President Harrison died just one month after taking office, and Tyler became the first vice president to succeed to the presidency. Amid uncertainty as to whether a vice president succeeded a deceased president, or merely took on his duties, Tyler immediately took the presidential oath of office, setting a lasting precedent. He signed into law some of the Whig-controlled Congress's bills, but he was a strict constructionist and vetoed the party's bills to create a national bank and raise tariff rates. He believed that the president, rather than Congress, should set policy, and he sought to bypass the Whig establishment led by Senator Henry Clay. Most of Tyler's cabinet resigned shortly into his term and the Whigs expelled him from the party, dubbing him "His Accidency". Tyler was the first president to have his veto of legislation overridden by Congress. He faced a stalemate on domestic policy, although he had several foreign-policy achievements, including the Webster–Ashburton Treaty with Britain and the Treaty of Wanghia with China. 