You’ve heard about Mitt Romney’s problems with the women’s vote, the black vote, the Hispanic vote, the union vote and the young Democrats vote. But there’s one major voting group that’s fallen off the map since the primaries.

The evangelical vote.

When Mitt Romney’s 2012 candidacy was gaining traction in the primaries, the conventional wisdom instantly conveyed that the evangelical vote, skeptical of Mormonism, would sink him.

What if in Ohio next week the opposite is true? There and in other swing states—Wisconsin, Iowa, North Carolina, Florida—the evangelical vote is flying beneath the media’s radar. It’s a lot of voters not to notice. In the 2008 presidential vote, they were 30% of the vote in Ohio, 31% in Iowa and 26% in Wisconsin.

ReutersMitt Romney meets with Billy Graham at his North Carolina home, Oct. 11.

Back in April, the policy director of the Southern Baptist Convention, Richard Land, predicted that evangelicals in time would coalesce behind Mitt Romney. Yesterday he endorsed Mr. Romney, the first time he has done so for any presidential candidate.

Ralph Reed, the president of the Faith and Freedom Coalition, has been spending a lot of time in states such as Ohio, Pennsylvania and Wisconsin in the belief that evangelical support for Mr. Romney could be decisive. He notes that when George W. Bush won Ohio in 2004, the Kerry camp thought their dominance of Democratic Cuyahoga County around Cleveland had the state locked up. But Mr. Bush’s solid support in evangelical-dominated counties from Cincinnati to the West Virginia border carried Ohio by two percentage points.

Before the first presidential debate on Oct. 3, Mr. Romney was eight points behind the president in Ohio. In the past week, the Cincinnati Enquirer/Ohio News Organization poll had Mr. Romney even with Mr. Obama, and a few days ago the Rasmussen poll put him up by two points.

Mr. Reed notes that in several opinion polls—NBC, Pew and ABC—the percentage of evangelicals claiming to support Mr. Romney has been in the mid-70s. “We estimate that in 2008 there were 350,000 evangelicals who didn’t vote in Ohio,” Mr. Reed says. “Obama carried the state by 260,000.” If that support of 70% or more holds for Mr. Romney in Ohio, and if the share of the evangelical vote increases by a point or two, then the challenger could carry the Buckeye State.

Also worth noting is that one of the biggest events of the 2008 election—the Saddleback Church interviews that evangelical Christian leader Rick Warren did with Barack Obama and John McCain—didn’t happen this year despite an offer from Mr. Warren. Mr. Obama’s effort in 2012 to reach out to these folks has been minimal. Mr. Romney met three weeks ago with the Rev. Billy Graham, who is actively supporting the governor. In May, Mr. Romney gave a well-received commencement speech on religious values at Jerry Falwell’s Liberty University.

Perhaps Mr. Obama concluded that the evangelical vote was his 47%. It’s generally thought that the president burned any remaining bridge to them with the gay-marriage decision that Joe Biden made for him. But it’s more complicated than one issue.

Four years ago, evangelicals mainly supported former Arkansas Gov. Mike Huckabee. When John McCain became the nominee, he and the evangelical community never connected, and many evangelicals stayed home. This time they are in motion.

The president of Ohio Christian University, Mark A. Smith, says, “The intensity of voters in the faith community is as high as I’ve seen it in the last 12 years.” The driver of that intensity is religious liberty. “We took a direct hit with the Affordable Care Act,” he says. Evangelicals watched the Obama administration’s big public fight with Catholic hospitals and charities. What they concluded is that the health-care law was a direct threat to their own private outreach programs.

Mr. Smith says that if evangelicals in Ohio’s rural communities repeat their turnout levels from 2000 and 2004, they will offset the Obama advantage in Cuyahoga County. “Six different faith groups are out there” for Romney in Ohio, he says. “That didn’t happen the last time.”

Mr. Smith and others I spoke to this week cited one more reason for their enthusiasm: Paul Ryan. Steve Scheffler, a longtime GOP activist in Iowa, says it was “the best possible choice” Mr. Romney could make for the ticket. “It galvanized evangelicals.”

Of course all this is also the reason Barack Obama can drill millions of campaign dollars out of Hollywood and Manhattan. This paranoid political money is missing a deeper issue in the 2012 campaign. In his campaign and his presidency, Barack Obama has been explicit about a historic enlargement of the nation’s public economy. For anyone whose life consists of making a living in private work and donating off-hours to private charity and private worship, there is a sense of being squeezed by this president. And among these are evangelical Christians.

Write to henninger@wsj.com