Robertson asked Bush about e-mails Clinton sent after the Benghazi attack, noting that administration officials had said at the time that the attack occurred during a spontaneous demonstration sparked by a video.
"Maybe the case could’ve been made that they thought they had enough security. Maybe," Bush said, urging accountability to the families of those who were killed.
“To spend this much time to get back to that basic truth, that in fact that it was not secure and the fact that it was a terrorist attack is unconscionable to be honest with you,” Bush said to the loudest applause of the afternoon.
Could Clinton be indicted? Robertson asked. “I’m going to pass on that one,” Bush said.
Bush also criticized his opponent businessman Donald Trump who said earlier this month that he would, on day one in office, send back thousands of Syrian refugees the U.S. accepts.
"America at its best defends the persecuted, who are acting on their faith no matter where they are in the world," Bush said.
Bush, who hopes to become the nation’s second Catholic president, made his appeal for the 2016 Republican presidential nomination to Robertson's largely evangelical audience, an important base for the Republican Party. He touched on social issues like abortion and made a pitch to Israel, a frequent issue of concern on Robertson's show.
"We have to re-establish America's leadership in the world, and if I had to pick the first place to start it'd be Israel," Bush said to applause.
Bush noted how he defunded Planned Parenthood when he was governor of Florida, saying that he believes Florida was the first state to provide government money to pregnancy centers.
"Religious freedom is at risk in all sorts of places," said Bush, who has made issues related to religious freedom a big part of his campaign.
He gave his faith testimony, telling the audience that he began to read the Bible and "realized Jesus is my savior" in the late 1980s. Bush, raised as an Episcopalian, joined his wife's Catholic Church in 1995 after he was defeated in his first run to be Florida’s governor.
Bush is the first Republican candidate in a series of candidate forums at the university. After Robertson's interview, an audience question-and-answer session with Bush was moderated by Jay Sekulow, head of the American Center for Law Justice, whose son, Jordan Sekulow, is Bush’s liaison to religious voters.
Former Virginia Gov. Bob McDonnell, who went to graduate school at Regent, was in attendance.
Republican-leaning white evangelicals, who hold sway in early primary states like Iowa and South Carolina, appear to favor businessman Donald Trump and Dr. Ben Carson.
Bush has struggled to harness the constituency that helped to boost his brother, who drew many evangelical voters with his story of giving up his partying ways after a talk with evangelist Billy Graham.
According to a Washington Post-ABC News poll conducted Oct. 15-18, 32 percent of Republican-leaning voters who are white evangelicals support Trump, compared to 32 percent of GOP voters overall. And 26 percent of Republican-leaning evangelicals support Carson, compared to 21 percent of GOP voters overall. Recent polls out of Iowa suggest that Carson is leading among evangelical voters there.
Bush announced Friday that he is shaking up his campaign with major spending cuts. The former Florida governor struggles among Republican voters in the polls and among donors.
“This means lean and mean and means I have an ability to adapt,” he told Robertson.
Bush said he has not met one person who thought Trump would be the frontrunner right now.
“God bless him for that success in that regard,” he said. "You have to adapt.”
During questions with the audience, Bishop Harry Jackson, a black pastor in Maryland, asked Robertson what his urban economic agenda would be if he were elected.
Robertson said the government should focus on strengthening security, family and schools. “Law enforcement should not be pulled back,” Bush said. “Build trust again, but there should be security.”
In May, Bush told CBN's David Brody he could not fathom the “warp speed” of changing public views on same-sex marriage. “Irrespective of the Supreme Court ruling … we need to be stalwart supporters of traditional marriage.”
Bush made a pitch to 13,000 evangelicals in Nashville in August in an interview with Southern Baptist leader Russell Moore, drawing attention for suggesting that “women’s health issues” could be overfunded.
In May, Bush gave the commencement address at Liberty University, urging religious conservatives to stand up to the federal government on matters on faith.
In April, Bush appeared on Focus on the Family's radio program, telling Focus president Jim Daly his “deeply held belief” is that “the most vulnerable in our society need to be protected. They need to have legal rights. And as a society, we need to recognize their value and their worth.”
For decades, Robertson, 85, has been an influential leader among evangelicals, especially among charismatic Christians. He founded the CBN, Regent University and the Christian Coalition. Robertson's past remarks, including a claimed that the 2010 earthquake in Haiti was God’s judgment, have drawn controversy even among evangelicals.
A significant number of Republicans have expressed concerns that Bush is too liberal, According to a Washington Post-ABC News poll conducted July 16-19. Of those surveyed, 33 percent of white evangelical Republican voters expressed concern. By comparison, 15 percent of evangelicals said Trump is too liberal, while 15 percent of evangelicals said the same of Rubio.