On September 12, 1960, less than two months before Americans would choose the next president of the United States, Democratic candidate John F. Kennedy was in Texas giving a speech to a Houston gathering of Southern Baptist clergy.

This wasn’t a normal campaign stop. Kennedy was Catholic and, at the time, only the second Catholic presidential candidate in U.S. history after Al Smith’s unsuccessful run in 1928. And for a Catholic candidate from New England, a conference of Southern Baptist ministers was considered ground zero for anti-Catholic political rhetoric and even outright bigotry.

“[C]ontrary to common newspaper usage, I am not the Catholic candidate for president,” Kennedy said on live TV in his now famous address. “I am the Democratic Party's candidate for president, who happens also to be a Catholic. I do not speak for my church on public matters, and the church does not speak for me.”

In the late 1950s, Catholic politicians were viewed with open suspicion by many mainline Protestants and Evangelicals. Shaun Casey, director of the Berkley Center for Religion, Peace and World Affairs at Georgetown University, and author of The Making of a Catholic President, says that Catholic candidates were accused of having “dual loyalties” to both the Vatican and the United States.

“The argument was, when push came to shove, a president who was Roman Catholic would ultimately be more loyal to the Vatican because the fate of his eternal soul was at stake,” says Casey. “If Kennedy was elected president, he’d criminalize birth control, he’d cut off foreign aid that helped countries invest in birth control, and he’d funnel tax money to Catholic parochial schools.”

When Al Smith ran for president in the 1920s, anti-Catholic sentiment was widespread. One political cartoon from the era shows Smith’s “cabinet” as a conference room full of bishops with the Pope sitting at the head of the table. Smith is seen serving the assembled clergy with a jug of “XXX” liquor. One prominent Baptist minister from Oklahoma told his parishioners, “If you vote for Al Smith you’re voting against Christ and you’ll all be damned.”

By the 1960 election, anti-Catholic bias was less overt, but still a considerable obstacle for Kennedy to overcome. Kennedy received hundreds of letters from conflicted Democratic voters saying that they loved his policies but could never vote for a Catholic, according to Casey.

Kennedy’s first challenge was to beat out Hubert Humphrey for the Democratic presidential nomination. There were 11 primaries in those days and Kennedy won the first nine, but barely took Wisconsin. Humphrey played up the fact that Kennedy won the predominantly Catholic districts in Wisconsin but lost the Protestant ones, proving that he could only win “the sectarian vote,” says Casey.

The real test came next: West Virginia, a state that was 95 percent Protestant. Humphrey was confident he would stomp Kennedy in the West Virginia primary, but JFK took his case directly to the voters. He bought a half-hour of local TV airtime on the Saturday night before the primary and assured the West Virginia voters of his commitment to the constitutional separation of church and state.

As Time magazine reported, a Kennedy pollster visited the home of an anti-Kennedy voter after the broadcast. "She took me in, pulled down the blinds and said she was going to vote for Kennedy now. 'We have enough trouble in West Virginia, let alone to be called bigots too.'"

Kennedy came back from 20 points down in the polls to win West Virginia and secure the Democratic nomination. The real fight came in the general election.

Richard Nixon and the Republican National Committee knew the Catholic question was one of Kennedy’s greatest weaknesses, and while Nixon professed publicly that he wouldn’t raise the issue of his opponent’s faith, his actions behind the scenes spoke differently.

“Nixon had a widespread, robust, anti-Catholic, pro-Protestant campaign that he was running surreptitiously,” says Casey. “People like Billy Graham and Norman Vincent Peale did a lot of organizing under the radar trying to gin up Protestant fear that this Catholic guy was going to be bad for them and bad for America.”

Graham and Nixon were in close correspondence in the run up to the election, and Graham, who was the most visible Evangelical religious figure in the country, was pulling out the stops for his candidate.

“I have just written a letter to my mailing list of two million American families, urging them to organize their Sunday school classes and churches to get out the vote[...],” Graham wrote Nixon in a letter. “We are getting other religious groups throughout the Nation to do the same; thus many millions will be personally circulated[...] It was also felt that this would bring about a favorable swing among these voters to you.”

According to Casey, Nixon quietly procured the services of a Missouri congressman named O.K Armstrong to recruit Protestant churches and anti-Catholic organizations like the Protestants and Other Americans United for Separation of Church and State, and Citizens for Religious Freedom to publish materials and give speeches about how a Catholic president would ruin America.

In September of 1960, Citizens for Religious Freedom organized a conference in Washington, D.C. featuring 150 prominent Protestant clergy including Norman Vincent Peale, author of the best-selling book The Power of Positive Thinking.

"Our American culture is at stake," Peale told the ministers. "I don't say it won't survive, but it won't be what it was."

In a statement, the Citizens for Religious Freedom wrote, "It is inconceivable that a Roman Catholic President would not be under extreme pressure by the hierarchy of his church to accede to its policies with respect to foreign relations... and otherwise breach the wall of separation of church and state."

The conference backfired—and Kennedy saw an opening. Casey said that if Nixon and his handlers hadn’t waged this secret anti-Catholic campaign against Kennedy, JFK would never have given that historic speech at the ministerial conference in Houston.

“I believe it was the power of that speech,” Casey says, “and the organizing that Kennedy did among protestants himself is what turned the election for him in the closing weeks.”