The conclusion that can be drawn from the fact that Millard Fillmore, the Know-Nothing candidate, received 21 percent of the popular vote in the election of 1856 is: A significant number of people were hostile toward immigrants.
The Know-Nothing Party, also known as the American Party, primarily focused on anti-immigrant and anti-Catholic sentiments during that period. Their platform largely appealed to those who were concerned about the increasing number of immigrants in the United States.