The Jacksonian Buchanan, who was re-elected in 1836 and 1842, opposed the re-chartering of the Second Bank of the United States and sought to expunge a congressional censure of Jackson stemming from the Bank War.[18]
During the contentious 1838 Pennsylvania gubernatorial election, Buchanan chose to support the Democratic challenger, David Rittenhouse Porter,[19] who was elected by fewer than 5,500 votes as Pennsylvania's first governor under the state's revised Constitution of 1838.[20][21]
Buchanan also opposed a gag rule sponsored by John C. Calhoun that would have suppressed anti-slavery petitions. He joined the majority in blocking the rule, with most senators of the belief that it would have the reverse effect of strengthening the abolitionists.[22] He said, "We have just as little right to interfere with slavery in the South, as we have to touch the right of petition."[23] Buchanan thought that the issue of slavery was the domain of the states, and he faulted abolitionists for exciting passions over the issue.[24]
His support of states' rights was matched by his support for Manifest Destiny, and he opposed the Webster–Ashburton Treaty for its "surrender" of lands to the United Kingdom. 