The Know Nothing National Convention nominated Fillmore for president, but disagreements over the party platform's stance on slavery caused many Northern Know-Nothings to abandon the party. Meanwhile, the 1856 Republican National Convention chose John C. Frémont as the party's presidential candidate. The defection of many Northern Know-Nothings, combined with the caning of Charles Sumner and other events that stoked sectional tensions, bolstered Republicans throughout the North. During his campaign, Fillmore minimized the issue of nativism, instead of attempting to use his campaign as a platform for unionism and a revival of the Whig Party.