Decades before the modern versions of the Democratic and Republican parties formed, the US also had a few other major political parties. One was the Federalists, led by Alexander Hamilton and John Adams. Another was the Whigs, who had intermittent success before collapsing in the middle 1800s. Out of the ashes of the Whig party two other parties rose to take its place: The anti-slavery Republican party, and the anti-immigrant American Party, better known as the Know-Nothings.
The Know-Nothings opposed immigration to the United States, particularly from Catholics. Anti-Catholic paranoia has a long history in the US. Catholics (the thinking went) were more likely to be loyal to the pope than the country they lived in, were unable to work with people whom they deemed to be “heretics” and were, in general, less hardworking and virtuous than their fellow Protestants. This xenophobia, paranoia, and bigotry was prevalent enough that in the election of 1856 the Know-Nothings would contend as a major political party, albeit a failed one.