The Know Nothing party was perhaps the most honest political movement ever to contest elections in the USA. Though officially known as the 'Native American Party' when the true Native Americans were described as 'Injuns, 'redskins' or 'Godless vermin', these particular WASP Know Nothings threatened to sweep American in the 1850s. They were an anti-immigration party, especially if the intruders came a Catholic country and believed in leprachauns. The Irish fitted both descriptions.
These original 'Know Knothings' claimed they were true patriots, tracing their origins to the Boston Tea Party when a fancy dress orgy had got out of hand and dumped British tea in Boston harbour. The 'K.N.' thereafter always looked at tea drinking as a distinctive anti-American attribute and would ban anyone who tried it as a beverage.
In the early 1840s the first proto Know Nothing party appeared. It was called - ahem - the American Republican Party. It was based in New York and kept it simple: No Immigration to the USA until American Republicans could work out what was happening in the world. Its main target were the Irish immigrants trying to escape hunger and a diet of mouldy potatoes. The party then changed its name to the Native American Party in 1845 and planned to run a presidential candidate in 1848 but failed to put in the nomination papers in time.
In the early 1850s the American Whig Party and Democratic Party were the dominant parties.Both were split with factionalism and attitude towards slavery (both had pro and anti slavery wings). When the Whigs fell apart in 1854 with some moving towards the anti-slavery Republican Party, others decided the real issue wasn't slaves but Catholicism and immigrants. This was a classic 'I want to fight battles on a territory of my choosing'. They joined they already existing Native American Party.
Rallying supporters against what you hated was a classic method of mobilising support. Know Nothings believed there was a vast conspiracy against the United States, co-ordinated by the Vatican. The Irish immigrants were just the point of the spear directed at the heart of their America. Since no Catholics had signed the Declaration of Independence, they were the religious enemy of old. The USA was for Protestant, English speakers only. In other areas of the USA the Catholic immigrant enemy were Hispanics in Mexico or Cuba. The Chinese immigrants in California were not Catholics but were considered 'pliable' to Catholic influence and a threat too.
United in what they feared and hated, the Know Nothings became hazy on the positive aspects of their political philosophy. It seemed simpler to express no views or that what they really believed in was a big secret that was not to be shared with outsiders. There was an elaborate code which would explain everything and the Republic would be saved by a re-animated George Washington who would descend from the clouds and re-set everything back to 1776. The Know Nothings with QAnon of their age.
As the Native American Party, they contested the 1852 Presidential election, coming in third behind the Democrats and Whigs. In 1855 the party dropped the 'Native' part of their political name. Their leader in that election was a former United States president Millard Fillmore. A former Whig, Fillmore had a long history of supporting conspiracies. In the 1830s he had belonged to the 'Anti-Masonic League' who believed the world was controlled by a shadowy cabal of men with criminal connections. Fillmore was therefore a good fit to lead the Know Nothings in the 1856 President elections. The coaliton of pro-cranks, ex-Whigs, unisex-Democrats and former-Common Sense fought against the Democrats and Republicans but still came in third.
Once again the Know Nothings tried to keep politics focussed on their paranoias but the issue of slavery and the fear that it was spreading in the USA was becoming more dominant. The Know Nothings began to break apart as the Whigs before them. Fear of Catholicism remained one constant, as former Whigs/Know Nothings joined the Southern Democrats in time for the American Civil War. They would latter give rise to the KKK.
The last major outing for the American Party was as part of a pro-Union alliance known as the Constitutional Union. This coalition of had no position on slavery or anything else except to preserve the United States. Its message was Vote for Us and Bury Your Head in the Sand. They found support in the border states between the Union and emerging Confederacy but broke apart soon after.
QAnon. Yes, the current 'Know Nothings' are these people. Conspiracy theorists on steroids.