COLUMBUS, Ohio -- While thousands streamed into a football stadium in Mobile, Alabama, to see Donald Trump Friday evening, a much smaller crowd of committed conservatives unwound at a bar here and mused over the good, the bad and the unknown of the unlikely Republican U.S. presidential front-runner. They were staffers and volunteers working for Americans for Prosperity (AFP), a nonprofit group funded by industrialist billionaire brothers Charles Koch and David Koch, two of the most effective conservative activists in U.S. politics.

According to AFP, 3,600 people came to this year's annual Defending the American Dream Summit from around the country Friday and Saturday, taking in appearances by a handful of the 17 Republican presidential candidates. Trump was not invited.

On the national level, Trump is dominating the contest for the 2016 Republican presidential nomination. He widened his lead over the crowded field in a Reuters/Ipsos poll Friday, with 32 percent of those surveyed saying they backed the billionaire.

But among this self-selected group of politically engaged conservatives, his popularity has yet to solidify. Trump the phenom dazzles, but Trump the candidate is getting the same scrutiny as the other 16 Republicans.

The apparent reticence among this influential grouping plays into one of the big political questions of the moment: Can Trump turn his strength in the polls and undeniable attractiveness to a certain slice of voters into victories in Republican primary elections early next year?

In the 2014 midterm elections, AFP achieved a 95 percent success rate in the election races where it spent money. As a nonprofit group, it cannot advocate for specific candidates, but it runs ads to defeat candidates who it believes are not doing a good job on specific issues.

'The Man’s A Jack---’

AFP President Tim Phillips told Reuters Saturday the group would keep its "laser" focus on advocating for issues such as tax reform, repealing the Affordable Care Act and fighting environmental regulations, no matter who is elected.

Former Florida Gov. Jeb Bush, U.S. Sen. Ted Cruz of Texas, Louisiana Gov. Bobby Jindal, former Texas Gov. Rick Perry and U.S. Sen. Marco Rubio of Florida were among the scheduled speakers. When it came to choosing candidates to invite to the summit, Phillips said, "We talked to people who had records that for the most part were philosophically aligned with us." He added, "We didn't want a cattle call.” He also noted that Trump had appeared at past AFP events.

AFP officials don't mince words about politicians they dislike, and Phillips recalled how AFP was critical of Cruz during the government shutdown two years ago.

Summit attendees did advocate for candidates, wearing preferences on T-shirts, hats and buttons, supporting the likes of Cruz and another candidate, retired neurosurgeon Dr. Ben Carson.

Although it wasn't hard to find people who said they liked Trump, the fervor that has driven the brash New York businessman to the top of the polls was a more reserved admiration here, an approval of the voice in the abstract rather than the candidate.

"It really frustrates me when he bashes other candidates -- and they're really cheap personal shots," said Althea Cole, 31, a Republican from Cedar Rapids, Iowa, who is a county chairwoman there for Carson's campaign. Still, she had some admiration for Trump's success. "The man's a jack---, but you don't get to be a billionaire by making friends," she said.

A group of college students in a Republican club at Augustana College in South Dakota felt he was too much of a bully. "He's mocking it with his presence," said Cara Beck, 20, as she stood with five male students between 19 and 21 years of age. Their picks were Bush, former Ohio Gov. John Kasich, U.S. Sen. Rand Paul of Kentucky and Rubio.

Among a group of young Tennesseans, Trump garnered mixed reactions -- plaudits for his business acumen, and boos for the reality-television star's showmanship. "Both my parents love Donald Trump, but I can't stand him," said Michael Stooksbury, 18, who likes Paul best. "He doesn't have any experience, he's just an entertainer."

However, Thomas Parham, 29, said the country could benefit from Trump's business background. "I'd rather us be a financial empire than an empire of war," he said. “That way we can take over country after country, territory after territory, without firing a single shot."

(Reporting by Emily Flitter; Editing by Mary Milliken)