RANCHO MIRAGE, Calif. — Three of the likely Republican presidential contenders decried the nation’s income gap and argued that President Obama deserves little credit for the improving economy in a forum Sunday night that offered a preview of the themes expected to dominate the 2016 election.

Sens. Ted Cruz of Texas, Rand Paul of Kentucky and Marco Rubio of Florida took part in a lively and at times wonkish discussion that ranged from economic policy to U.S. policy toward Iran to the role of wealth in politics. Their 80-minute conversation marked the first time that a crop of potential White House contenders shared a stage in the 2016 season, a session that exposed some of the fault lines that will separate the crowded GOP field.

The panel, moderated by ABC News Chief White House Correspondent Jonathan Karl, took place at a private meeting of wealthy donors hosted by Freedom Partners, a tax-exempt group that serves as the hub of a political network supported by Charles and David Koch and other conservative financiers. In a first, the organization shared a live Web stream of the event with news organizations.

The senators alluded to the vast resources of their well-heeled audience even as they called for new economic policies they said would lift up a struggling middle class. Those who are doing well are “the top one percent, the millionaires and billionaires the president loves to demagogue, one or two of whom are here with us tonight,” Cruz said, adding: “The people who have been hammered for the last six years are working men and women.”

Cruz dismissed the economic gains that Obama touted in his recent State of the Union speech as “the description of an alternate reality. I chuckle every time I hear Barack Obama or Hillary Clinton talk about income inequality, because it’s increased dramatically under their policies,” he said.

Paul agreed. “The reason I would say the economy is getting better is despite the president and despite the president’s policies,” he said, crediting the lift instead to revenues from oil and gas extracted from private land. “This president should take no credit for any kind of recovery we have,” he added to hearty applause.

Rubio said taxes and regulations have held back the ability of the United States to compete on a global stage, adding that more higher-wage jobs were needed to address income disparity. “The best cure for poverty is a job, a good paying job, and our economy isn’t producing enough of them,” he said.

The Democratic National Committee challenged their arguments, citing the country’s recent job growth, low gas prices and stock market gains in one of several e-mail statements the party blasted out during the forum.

While Cruz, Paul and Rubio sounded similar notes on the economy, the trio divided sharply over foreign policy.

Paul and Rubio quarreled over Obama’s recent announcement that the United States would begin taking steps to normalize relations with Cuba.

“I grew up in a family that was about as anti-communist as they come,” Paul said, but added: “We’ve tried an embargo for 50 years. It hasn’t worked.”

Rubio challenged the notion that the change in U.S. policy would bring democracy to the island, warning, “Cuba is 90 miles from our shores… what happens there we will feel immediately.”

And the three senators got in a heated debate about U.S. negotiations with Iran over its nuclear program.

“I am a little cautious, I would say, perhaps skeptical about negotiating with someone who has openly said he wants to force all of us to either be like him or die,” said Rubio, referring to Ayatollah Ali Khamenei, the country’s supreme leader.

Cruz echoed that view, calling referring to Khamenei and the country’s mullahs “radical religious Islamic nutcases – and that’s the technical term.”

Paul took a more measured tone. “I do not trust the president, I don’t believe or support him on almost anything he does,” he said, “but at the same time, I think diplomacy is better than war and we should give diplomacy a chance.”

All three jabbed at former Secretary of State Hillary Rodham Clinton, who is expected to be the dominant contender for the Democratic presidential nomination. Paul referred to “Hillary’s war in Libya” as “a disaster.” Rubio said it would be “a mistake to elect as president the architect of Obama’s foreign policy.”

The GOP’s last presidential nominee, Mitt Romney, came in for more praise, but Paul and Cruz dismissed the idea that he could succeed in a third bid for the White House.

“To win the presidency you have to reach out and appeal to new constituencies and I just don’t think it’s possible,” Paul said. “If he thinks, ‘I’ll just change a few themes’ -- I think it’s just a little more visceral, how you connect with people.”

Cruz said that Romney’s infamous 47 percent comment sent the wrong message about the priority of Republicans. “What the voters heard was we don’t have to worry about the 47 percent,” said the Texas senator. “And I think Republicans are and should be the party of the 47 percent.... we should be fighting for the little guy.”

Rubio, meanwhile, took a not-so-veiled swipe at governors such as Scott Walker of Wisconsin, who plans to take a trade mission to London next month as he ramps up his own expected presidential candidacy. “Taking a trip to some foreign city for two days does not make you Henry Kissinger,” the Florida senator said.

Karl pressed the senators on the role of the super wealthy in politics, noting that they were speaking before the Kochs and other rich conservative patrons. How would they ensure they would not be beholden to those who spend large sums to help elect them to office?

“Most of the people that support us support us because they agree with what we’re doing, not because we agree with what they’re doing,” Rubio responded, adding: “I don’t know a single person in this room who has ever been to my office … asking from government any special access. By and large what they want is to be left alone.”