BURLINGTON, Iowa (Reuters) - Beto O’Rourke made his debut as a Democratic presidential candidate on Thursday, betting his optimistic economic message, liberal immigration policies and fame gained in a failed bid for the U.S. Senate last year will net him the party’s 2020 nomination.

The former U.S congressman from El Paso, Texas, who announced his White House run by video on social media, immediately kicked off a three-day campaign swing through Iowa, which hosts the nation’s first nominating contest in less than a year and is critical to his chances.

“The challenges have never been greater, or more severe, or more critical or more defining for our future,” he told an enthusiastic crowd at a coffeehouse in Burlington.

O’Rourke, 46, joined a jam-packed field of more than a dozen Democratic candidates, including several U.S. senators. It remains to be seen whether he can make up ground for his relatively late entry into the race.

Critics say O’Rourke lacks a deep policy background and his unsuccessful run against U.S. Senator Ted Cruz of Texas last November disqualifies him from pursuing an even higher office.

Still, his underdog race against Cruz earned him a national following. Even in defeat, O’Rourke demonstrated a talent for attracting capacity crowds and raising large sums of money, skills he will need to carry to the national stage if he is to capture the nomination.

O’Rourke jumped atop the coffee shop’s counter and delivered an impassioned address, touching upon issues of economic inequality, climate change and education. He largely avoided criticizing President Donald Trump by name but made his opposition to Trump’s policies clear.

He also avoided any allusions to the Democratic field - or his own chances in the race. Asked by an attendee what made him stand out from the pack, he demurred. “All I can tell you is who I am,” he said. He cited his ability to work with Republicans in Congress and the Trump administration.

Trump, who became known for slapping derisive nicknames onto opponents during the 2016 campaign, focused on O’Rourke’s hands on Thursday when asked about O’Rourke’s campaign announcement.

Slideshow ( 11 images )

“Well, I think he’s got a lot of hand movement. I’ve never seen so much hand movement. I said, ‘Is he crazy or is that just the way he acts?’,” Trump said during an Oval Office appearance with Ireland’s prime minister.

RESHAPING THE RACE

Unlike many of his opponents who launched campaigns while barely registering in public opinion polls, O’Rourke begins in sixth place in the RealClearPolitics average of polls, receiving an average of 5 percent.

But O’Rourke is far from a front-runner, with Senator Bernie Sanders of Vermont and former Vice President Joe Biden, who is considering a White House bid, leading polls.

It remains to be seen how O’Rourke, a white male with a history of supporting some moderate positions in Congress, will fare in a Democratic nominating battle with a heavy emphasis on progressive policies and diversity.

He lands squarely in the middle of an internal party debate about whether to nominate a liberal firebrand or a centrist, and he will face a test on whether he can match up with policy heavyweights like Senator Elizabeth Warren of Massachusetts.

Tom Courtney, a former Iowa state senator and the local chairman of the Democratic Party, said O’Rourke could reshape the race.

“Him coming into the race could dry up money for some of the others,” said Courtney, who is neutral in the party primary. “Some of the candidates who didn’t have too good a chance just might drop out.”

Slideshow ( 11 images )

Shea McCuen, 36, of Burlington, expressed concern that O’Rourke was too unestablished and progressive and risked alienating traditional Democrats. He said he might make a better vice presidential nominee alongside someone such as Biden.

“Going too young or too new, you’re going to lose some of the older Democrats,” McCuen said.

Dawn Hecox, 65, of Fort Madison, Iowa, said O’Rourke reminded her of a young Barack Obama when he ran in Iowa as a presidential candidate in 2007.

“He has really fresh ideas,” Hecox said.

“This election I am looking at who can beat Trump,” she added. “We don’t need what we’ve got in Washington right now.”

O’Rourke is the 15th Democrat in the field and the second from Texas, and his opponents took notice. U.S. Senator Kamala Harris of California sent an email fundraising appeal to her supporters on Thursday that had his name in the subject line.

“He injects a lot of excitement, but I also think he has a huge bar to meet,” said Democratic strategist Maria Cardona, who worked on presidential campaigns for Hillary Clinton and Barack Obama. “The expectations for him are so high that it’s going to be tough not to disappoint some people who are now seeing him through rose-colored glasses.”