By Gram Slattery and James Oliphant

WASHINGTON (Reuters) -Former U.S. President Donald Trump and Florida Governor Ron DeSantis made their cases to evangelical voters who gathered in Washington for a pair of events on Friday, seeking an edge with a voting bloc likely to play a pivotal role in selecting a 2024 presidential nominee.

The pressure was all on DeSantis, who trails Trump in the Republican presidential primary by nearly 40 percentage points in most opinion polls, including among evangelical voters.

Both candidates spoke at a pair of national summits convened by the Concerned Women of America and the Family Research Council, evangelical advocacy groups that support laws restricting abortion, among other issues.

At the Family Research Council event, DeSantis defended allowing churches to remain open in Florida during the COVID-19 pandemic, drawing cheers from the ballroom crowd.

"We protected our religious institutions when so many states were running roughshod over people's rights to practice their faith in full," he said.

He also talked up Florida's law that bans abortion at six weeks, among the most restrictive in the nation. "We have stood up," he said.

Across town, Trump also addressed the abortion issue, saying that he supports bans with exceptions for rape, incest and to save the life of the mother, a position that was received coolly by the crowd.

"I think its very hard politically if you don't," Trump said. "We have a lot of election losses because of this, because (other Republicans) don't know how to discuss it."

The longtime president of the council, Tony Perkins, a prominent evangelical leader, did not endorse Trump during his 2016 campaign and has yet to endorse a candidate this time around.

Trump holds a roughly 35 percentage-point lead over DeSantis and Vivek Ramaswamy among evangelical Christians, according to a Reuters/Ipsos poll that closed on Thursday.

Those voters have stood by the twice-divorced Trump even as he rarely invokes scripture or speaks with an evangelical bent and as he has faced a series of charges involving attempts to overturn the 2020 presidential election and a scheme to pay "hush money" to a porn star.

Many Christian activists credit him for helping to bring an end to nationwide abortion rights by appointing three conservative justices to the U.S. Supreme Court, which last year overturned the landmark 1973 Roe v. Wade decision.

Robert Goss, 77, a retired law-enforcement officer from Locust Dale, Virginia, was awaiting Trump and DeSantis at the Family Research Council event, saying he was still deciding which candidate to support.

Goss said he could be persuaded to vote for Trump again, but "he's got to get past all the legal things. And I just don't want four more years of nothing but fighting and bickering. We want to get something done."

He said he was also considering DeSantis, but "whoever was advising him probably should have told him to wait until '28. It's bad timing."

Hannah Bruce, 25, a political organizer from Idaho who attended the women's event in Washington, said she was initially interested in DeSantis, but she and most of her peers had turned back to Trump.

"I really was thinking DeSantis would be a perfect person because he's young, he's vibrant. He could have been a new JFK," Bruce said, referring to popular Democratic President John F. Kennedy during the 1960s. "But he wasn't."

DeSantis' advisers are betting he can eat into Trump's significant polling lead by outperforming among devout Christians, especially those who are affluent and well-educated, according to several people familiar with his strategy.

That could be a major factor in the state of Iowa, where white evangelical voters are expected to turn out in large numbers in the first 2024 Republican nominating contest four months away.

On Thursday, DeSantis unveiled a "Faith and Family Coalition" of more than 70 faith leaders backing him in Iowa, New Hampshire and South Carolina. All are among the first states to cast ballots in the Republican nominating process.

On Saturday, DeSantis and several other Republican primary contenders are due to speak at the Iowa Faith and Freedom Coalition's fall banquet in Des Moines, another major gathering of religious conservatives. Trump, who has a rocky relationship with some key political figures in Iowa, will not attend.

(Reporting by Gram Slattery and James OliphantAdditional reporting by Jason LangeEditing by Colleen Jenkins, Howard Goller and Kim Coghill)