The Know-Nothing Party got its start in New York in the 1840s. The movement spread to other states and in 1845 nativist groups united as the Native American Party. (Nothing to do with what we now call Native Americans, of course.) In 1855 they renamed themselves simply the American Party, but throughout this time they were popularly known as the Know-Nothing Party, and that name even appeared on ballots.
The Know-Nothings gained strength from the demise of the Whigs and concern over immigration. Their platform called for severe restrictions on immigration, a 21-year wait for naturalization, barring foreign-born citizens from public office, and the employment of only Protestants as teachers in public schools. Their main concern was the growing number of Catholic Irish and German immigrants, who, they maintained, could never be true Americans, since they were under the control of priests and the Pope. This animosity was coupled to dissatisfaction with the career politicians of the Whig and Democrat parties who had not controlled immigration and had not solved the problems of slavery and sectionalism.
In California the concern was not as much about Irish and German immigration, as the influx of Chinese and South American immigrants. But at the bottom was the same fear of the “other” and the desire to keep California (and America) for Americans. Like their Eastern brethren, Californian voters were unhappy with incumbent politicians. Two-term governor John Bigler, who was running for a third term on the Democratic ticket, was seen as responsible for the growing state indebtedness. It was time for new blood.
The Know-Nothing Party put up as their candidate Assemblyman J. Neely Johnson. He won and was described as “the most startled man in the state” when told of his election. (Where that quote comes from I do not know, but every source online quotes it.) At thirty years old, he was the youngest man to ever be elected as governor of California.
The Know-Nothings did well in the 1855 election. Several senators and assemblymen were elected on their ticket, as well as the mayor of San Francisco.
Unfortunately, it was the wrong year for John Bidwell to decide to run again for the state senate as a Democrat. According to Gillis and Magliari:
Campaigning to recapture his old senate seat, Bidwell carried Butte County with just sixteen votes to spare against his Know-Nothing opponent, John B. McGee. Bidwell’s narrow margin in Butte was eclipsed, however, by McGee’s majority in neighboring Plumas County, which comprised the second half of the Fourteenth Senate District. (John Bidwell & California, by Michael J. Gillis & Michael F. Magliari, p. 186.)
Although the Know-Nothings faded quickly after that, Bidwell never again tried to run for the state senate. Instead, he left the Democratic Party (when it fell apart in 1860) for the new Republican Party, and in 1864 was elected to the United State Congress.