Jonathan Zimmerman is a professor of history and education at New York University. He is the author of “Small Wonder: The Little Red Schoolhouse in History and Memory” (Yale University Press).

Many years ago, one of my best history teachers gave me advice I have never forgotten. “Don’t just listen to what people say,” he urged. “Listen to what they leave out, too.”...

...Gingrich and Mr. Santorum [are not, like the Mormon Mitt Romney,] evangelical Christians.... They’re Catholics.

Their evangelical backing is a truly astonishing fact, given the long history of anti-Catholicism among evangelical Protestants in America. For more than three centuries, Evangelicals insisted that Catholicism represented a mortal threat to the body politic. But over the past three decades, they have joined hands with their former foes to change the face of politics altogether....

By 2004, when the Democrats nominated Massachusetts Sen. John Kerry for president, Evangelicals praised the Catholic bishops who threatened to deny communion to Senator Kerry because of his support for abortion rights. That same year, a survey of Evangelicals showed Pope John Paul II with higher approval ratings than either Jerry Falwell or Pat Robertson, both stalwart Protestant televangelists....

And that might be good news for – of all people – Mitt Romney. A recent Vanderbilt University study showed that nearly one-third of Southern Evangelicals said they would not vote for a “qualified Mormon” for president. But when the same respondents were asked how they’d vote if Romney faced off against President Obama, fully 85 percent said they would cast their ballots for Romney – a Mormon....