They slammed him for not labeling Islamic State terrorists followers of radical Islam. They criticized him for not combating the threat of terror forcefully enough and for inking a nuclear deal with Iran they dismissed as weak. And they argued he is not taking seriously the threat posed by Syrian refugees.
The event served as a key audition before an influential part of the Republican electorate in Iowa: Evangelical Christians. Bob Vander Plaats, head of the Family Leader, the Christian conservative group who hosted the event, called it a "final exam" before he makes an endorsement.
Cruz, a Texas senator who has clashed sharply with Obama this week over Syrian refugees, was one of the most aggressive critics of the president, charging Obama's actions in Libya and Egypt, among others things, have helped enemy combatants.
Asked what he would say to Obama if he were sitting near him, Cruz gestured to the packed crowd and said: "Mr. President: This is America."
Cruz also referenced a comment Obama made during the 2008 campaign about people clinging “to guns or religion.”
“He can’t have either our God or our guns,” said Cruz, who was received well at the event and held a large reception afterward with Rep. Steve King (R-Iowa), who backs him.
Rubio, a Florida senator who has accused Cruz this week of being soft on national security because he voted to limit the government’s surveillance capabilities, also focused his attacks on Obama.
When Frank Luntz, the Republican pollster who moderated the discussion asked him why Obama is not using the strategy Rubio advocated, Rubio responded flatly: “Well, he’s a bad president.”
Obama's support for Syrian refugees was also a target.
“The thing is, we can't be blind and say there is no threat,” said Sen. Rand Paul (R-Ky.).
Protesters interrupted the event twice. At the very start, immigration activists chanted, "Deportation's anti-family!" and held up a large banner near the stage. Later, animal rights activists yelled "It’s not food! It’s violence!"
"I feel like this is being conducted in Berkeley, California," quipped Luntz after the second batch of protesters were removed.
At the outset, Luntz made sure to point out that the event was not a debate but a forum. The candidates were seated at a long table meant to resemble Thanksgiving dinner. Luntz called them by their first names in an effort to keep the conversation casual.
"No buzzers, no bells, no gotcha questions, no moderators that you hate,” he said, explaining the format.
Luntz admittedly broke from his own format when he asked for a show of hands of from those who believe Secretary of State John Kerry should resign after Cruz called for it. But former Arkansas governor Mike Huckabee objected and the exercise fizzled.
The candidates also weighed in on social issues, voicing strong opposition to gay marriage and abortion. They argued that religious liberties must be protected.
Toward the end, the discussion turned personal and emotional. Former Hewlett-Packard chief executive Carly Fiorina and former senator Rick Santorum talked about the death of their children. Cruz discussed the toll his parents’ divorce took on him.
As the race grows nastier, Friday's gathering was a a respite from the political combat that is becoming more prevalent in the race by the day.
Can Republicans disagree without being disagreeable?
“I think the answer is: sometimes," said Paul.