Republican presidential candidate Donald Trump speaks at the Family Leadership Summit in Ames, Iowa, July 18, 2015.
Republican presidential candidate Donald Trump speaks at the Family Leadership Summit in Ames, Iowa, July 18, 2015.

Ten Republican U.S. presidential hopefuls began auditioning Saturday in front of huge crowds in the state of Iowa, hoping to win support from a key Christian conservative coalition.

The candidates were appearing in Ames at an annual family leadership summit — a grouping of influential evangelical voters seen as key to winning the state's coveted presidential caucuses early next year.

Analysts see no clear favorite among the candidates: Scott Walker, Donald Trump, Rick Santorum, Marco Rubio, Rick Perry,  Bobby Jindal, Mike Huckabee, Lindsey Graham, Ted Cruz and Ben Carson. Summit organizer Bob Vander Plaats said support could eventually be split among several candidates.

At Saturday's event, Trump drew boos from the crowd when he said Arizona Senator John McCain, who was a Navy pilot during the Vietnam War and was held as a prisoner of war for more than five years, "is a war hero because he was captured."  He went on to say, "I like people who weren't captured."

At a news conference a short time later, Trump did not apologize for the remarks.  But he added that "if a person is captured, they're a war hero as far as I'm concerned ... but you have to do other things also."

Iowa's evangelical voters, known for their tight organization and strong turnout at the polls, have traditionally influenced the outcome of the state's Republican presidential caucuses.   

Democrats' event

Democrats have also stepped up their campaigns in the bellwether state, with all five candidates attending a party fundraising dinner Friday in Cedar Rapids.

Democratic presidential candidate Hillary Rodham C
Democratic presidential candidate Hillary Clinton speaks during the Iowa Democratic Party's Hall of Fame Dinner in Cedar Rapids, Iowa, July 17, 2015.

Current party front-runner Hillary Clinton took aim at Republican rivals, saying she was "never going to let Republicans rip away the progress we have made."

She accused Republicans of backing an ineffective formula for for governance.  "Cut taxes for the super wealthy, let big corporations write their own rules.  That's it," she told the crowd of 1,300 cheering donors.

"Trickle-down economics has to be one of the worst ideas of the 1980s," she said, evoking Republican policy from the Ronald Reagan era. "It is right up there with New Coke, shoulder pads and big hair."  

Key Democratic themes addressed at the dinner included the fight against wealthy special-interest groups and battles in support of gay rights, women's rights, immigration reform and increased spending on infrastructure projects.  

Bernie Sanders, a left-leaning candidate, told the audience that economic equality is the moral, economic and political issue of our time.  "The greed of the billionaire class has got to end," he said. But he also warned that "nothing will get done unless millions of people loudly proclaim enough is enough."

Recent polling shows Sanders climbing in popularity, and he has attracted larger audiences in recent days than Clinton has.

The Clinton campaign has signaled that it considers Sanders to be a legitimate challenger who will be running for the long haul, noting the $15.2 million he's raised — largely from small donors — in the first three months of the race.

They believe he will find a measure of support in Iowa, where the caucus system typically turns out the most passionate voters, and in New Hampshire, given Sanders' many decades representing neighboring Vermont in Congress.

Maryland governor

Former Maryland Governor Martin O'Malley, a strong advocate for environmental causes, presented himself as the only candidate with 15 years of executive experience.  He touted his successful push to grant driver's licenses to undocumented immigrants and his campaign to ban the sale of assault weapons.

But like Sanders, O'Malley got some of his biggest applause when he talked about regulating and punishing Wall Street — underscoring the populist mood of the most active Democratic voters.

"Main Street struggles while Wall Street soars," he said. "If a bank is too big to fail, too big to jail and too big to manage, then it's too damn big."

The fundraiser marked the first time that all five Democrats running for president have appeared together. Along with Clinton, Sanders and O'Malley, former Rhode Island Governor Lincoln Chaffee and former U.S. Senator Jim Webb have declared they are seeking the Democratic Party nomination.

Some information for this report came from AP.