Republican presidential candidate Donald Trump told conservative pastors in Florida, Aug. 11, that if he's elected, they will "have great power." Trump pledged to take on a law that bars tax-exempt organizations from getting involved in political campaigns. (The Washington Post)

Donald Trump urged evangelical Christians to rally behind him in a speech here Thursday, seeking to ease their concerns about the Republican presidential nominee and proclaiming that sending him to the White House is crucial for the future of their movement.

Trump tried to draw a direct distinction between himself and Mitt Romney, the party’s 2012 nominee, who would have become the nation’s first Mormon president. Echoing some post-2012 analysis suggesting that Romney’s religion led some evangelicals to stay home, Trump said “religion didn’t get out and vote” for the former governor, “whatever the reason.”

Throughout the day, Trump also intensified his attacks against Democratic rival Hillary Clinton and President Obama, repeatedly casting them as co-founders of the Islamic State terrorist group as a result of their Middle East policies.

Adding to party leaders’ worries, Trump signaled in a television interview that he does not intend to change the way he campaigns, despite fears that his proclivity for picking distracting fights could cost him the election.

Here in Orlando, he spoke to leaders of evangelical Christian groups, some of whom have privately expressed skepticism about Mormons. Trump stressed his difficulties in the country’s only majority-Mormon state — making an apparent play for support by noting that he has a “tremendous problem” in Utah.

These 10 states are in play in the 2016 election. Here is where they're polling as of August and how much weight they'll have in November. (Sarah Parnass/The Washington Post)

The New York real-estate developer told the audience, a gathering of influential pastors hosted by the American Renewal Project, that they have a “chance to do something that will be earth-shaking” this fall. But they must ensure strong turnout at the polls, he said.

“You’ve got to get your people out to vote,” he said.

Trump called Utah “a different place” and asked whether anyone in the crowd was from the state.

“I didn’t think so,” he said. Some laughed.

Trailing in the polls, Trump can ill-afford to lose support among Christian conservatives nationwide. He must find a way to prevent Utah from slipping away as he faces a daunting electoral map with little margin for error.

“We’re having a problem,” Trump repeated. He added that he has been “given a false narrative.”

Recent polls have shown Clinton within striking distance of Trump in Utah. Trump’s brash style appears to have turned off much of the state’s large Mormon population, as it did during the GOP primary campaign. Trump lost badly to Sen. Ted Cruz (Tex.) in Utah’s Republican caucuses.

The last time a Democratic presidential candidate won Utah was the landslide election of 1964, when President Lyndon B. Johnson easily defeated Republican Barry Goldwater.

With a subdued tone and a suggestion that a winning presidential campaign could get him into heaven, Trump spoke for 40 minutes Thursday afternoon to the crowd of 700 pastors and their spouses. He drew a standing ovation and occasional shouts of “amen” as he promised to restore the vigor of church life.

Trump was squarely in businessman mode, staying away from theology and divisive social issues during his address, instead suggesting that the church had lost its leverage and its popularity because of government interference.

He offered a simple formula to bring back the power of religion: repealing a federal rule that limits churches and other tax-exempt organizations from participating in electoral politics.

“You’ve lost your voice,” Trump told the audience of church leaders. “We’re going to get it back.” He then dove into the history of an amendment introduced in the 1950s by then-Sen. Lyndon B. Johnson (D-Tex.) that limited electoral activity by tax-exempt groups.

His message resonated with this particular group of clerics, who gathered in Orlando to receive training in encouraging political activity by conservative church members.

Trump proudly announced that he scrapped plans to deliver a scripted “ho-hum” speech in favor of giving a more casual talk.

“Did you notice I took the teleprompters down?” he asked.

Trump credited evangelicals during his convention speech last month for their role in his campaign, saying, “The support they have given me, and I’m not sure I totally deserve it, has been so amazing.”

Still, evangelical Christian leaders have been split over the Republican nominee, in part because of concern about his coarse comments about women, immigration and other topics. Russell Moore, president of the Southern Baptist Convention’s Ethics & Religious Liberty Commission has called Trump’s campaign “reality television moral sewage.”

At times in his Thursday speech, Trump diverted to other issues, including foreign policy. He repeated his claim, leveled throughout the day, that Obama and Clinton are responsible for the rise of the Islamic State.

“Last night, you said the president was the founder of ISIS. I know what you meant. You meant that he created the vacuum, he lost the peace,” conservative radio host Hugh Hewitt told Trump during a morning interview, using an acronym for the terrorist group.

Trump responded: “No, I meant he’s the founder of ISIS. I do. He was the most valuable player. I give him the most valuable player award. I give her, too, by the way, Hillary Clinton.”

What is now known as the Islamic State was founded by Abu Musab al-Zarqawi, and was active in Iraq by 2003, when then-Secretary of State Colin L. Powell cited him in a speech to the United Nations.

“It goes without saying that this is a false claim,” Clinton adviser Jake Sullivan said in a statement responding to Trump.

In an interview with CNBC, Trump called himself a “truth-teller” and sounded content to keep campaigning as he has, embracing new feuds each week that many Republicans think distract from Clinton’s unpopularity.

“If at the end of 90 days, I’ve fallen short . . . even though I’m supposed to be the smart one and even though I’m supposed to have a lot of good ideas, it’s okay. I go back to a very good way of life,” he said.

Trump’s performance in Orlando was hailed by several of the pastors and by David Lane, the founder of the American Renewal organization. Lane is planning an $18 million effort to mobilize evangelical voters in battleground states to support Trump and the rest of the GOP ticket.

“Turnout is everything, and Donald Trump understands that,” said Lane, who spoke briefly with the candidate before his speech and agreed to help him win evangelical voters, a constituency considered vital to Republican success.

Lane complimented Trump on his practical approach, which at times drew on his experience with the vocabulary of business.

“This was not Donald Trump’s natural constituency,” Lane said, but he impressed the audience with his discussion of the decline of churches and the need to “leverage” opportunities such as an election.

Trump was introduced by an adored figure at such meetings, Mike Huckabee, a former Arkansas governor and a pastor himself who alluded to the religious liberty theme that ignites the interest of conservative pastors.

Huckabee said that Trump must win in November because it is “the most important election of our lifetime. It is about protecting the last castle on Earth where freedom lives.”

When Trump took the stage, he echoed that sentiment.

“Once I get in, I will do my thing that I do very well. And I figure it is probably, maybe the only way I’m going to get to heaven. So I better do a good job.”

Sullivan reported from Washington.