The first Republican National Convention that nominated candidates was held in 1856 in Philadelphia, and John Frémont was chosen to run for the U.S. presidency. Frémont, running on a platform that opposed slavery (as well as polygamy in Mormon areas), was one of the many military heroes nominated by the political parties (John Kerry and John McCain being the last two). At this convention, Abraham Lincoln lost in the balloting for the vice-presidential nomination to William Dayton, who had been a U.S. senator from New Jersey.

During the Mexican-American War, Frémont captured Santa Barbara, California, and later served as a senator of California, after it became a state. One campaign poster depicted the Republican candidate on horseback [illustrated in the upper-right box]—a common image-management technique, which had been used in previous U.S. campaigns for candidates with military backgrounds, including Andrew Jackson. Frémont looks almost Napoleonic here (second only to William Henry Harrison sixteen years earlier [shown in the lower-right box]), but his regalia are those of a frontiersman—to appeal to a large segment of the American electorate then.

Frémont lost to James Buchanan, the nominee of the Democratic Party, by a 12% margin, with ex-President Millard Fillmore, of the anti-immigrant American (or "Know-Nothing") Party, trailing by almost 24 points.