Buchanan's support was otherwise reduced to a narrow base of southerners.[65][71]
The division between northern and southern Democrats allowed the Republicans to win a plurality of the House in the 1858 elections, and allowed them to block most of Buchanan's agenda. Buchanan, in turn, added to the hostility with his veto of six substantial pieces of Republican legislation.[72] Among these measures were the Homestead Act, which would have given 160 acres of public land to settlers who remained on the land for five years, and the Morrill Act, which would have granted public lands to establish land-grant colleges. Buchanan argued that these acts were unconstitutional.[73]

Foreign policy
Buchanan took office with an ambitious foreign policy, designed to establish U.S. hegemony over Central America at the expense of Great Britain.[74] He hoped to re-negotiate the Clayton–Bulwer Treaty, which he thought limited U.S. influence in the region. He also sought to establish American protectorates over the Mexican states of Chihuahua and Sonora, and most importantly, he hoped to achieve his long-term goal of acquiring Cuba. After long negotiations with the British, he convinced them to cede the Bay Islands to Honduras and the Mosquito Coast to Nicaragua. 