However, as the war came to an end, Buchanan argued for the annexation of further territory, and Polk began to suspect that he was angling to become president. Buchanan did quietly seek the nomination at the 1848 Democratic National Convention, as Polk had promised to serve only one term, but Senator Lewis Cass of Michigan was nominated.[26]
Ambassador to the United Kingdom
Bust of James Buchanan by Henry Dexter at the National Portrait Gallery
With the 1848 election of Whig Zachary Taylor, Buchanan returned to private life. He bought the house of Wheatland on the outskirts of Lancaster and entertained various visitors while monitoring political events.[27] In 1852, he was named president of the Board of Trustees of Franklin and Marshall College in Lancaster, and he served in this capacity until 1866.[28] He quietly campaigned for the 1852 Democratic presidential nomination, writing a public letter that deplored the Wilmot Proviso, which proposed to ban slavery in new territories. He became known as a "doughface" due to his sympathy toward the South. 