SIOUX CITY, Iowa (Reuters) - Senator Elizabeth Warren informally kicked off the 2020 Democratic presidential nominating fight on a weekend visit to Iowa, condemning the corrupting influence of money on politics and lamenting lost economic opportunities for working families.

In the state that holds the first presidential nominating contest in 13 months, Warren introduced herself to Iowa crowds with tales of her working-class upbringing in Oklahoma and emphasized her signature theme of income inequality.

“Washington works great for those with money but not for anyone else. We need to call this what it is, corruption pure and simple,” the Massachusetts senator told Democrats in Sioux City on the second of five public stops during her three-day visit.

It was an early jump on the race for Warren, who formed a presidential exploratory committee and began hiring staff this week. So far she is the biggest name to enter what promises to be a crowded Democratic field, with at least two dozen others considering a run.

Former Housing Secretary Julian Castro also has formed an exploratory committee, and former U.S. Representative John Delaney became the first Democrat to formally declare last year and has campaigned extensively in the state.

But Warren, 69, had Iowa to herself this weekend, and she used the time to make contacts with prominent state activists and court crowds with promises to fight what she called a rigged economic system that favors the wealthy.

“These are dangerous times for our country, and Iowa is going to play a big part in determining where we go next,” said Warren.

She has been one of the most outspoken critics of President Donald Trump, a Republican, but rarely mentioned him by name at her public events on Friday and Saturday.

In the Senate, Warren is also an outspoken critic of Wall Street and is a leader of the party’s progressive wing, but she could face competition in the nomination fight from other liberal voices such as fellow Senators Bernie Sanders and Kamala Harris.

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Democrats face lingering tensions between their most liberal voices such as Warren and the more pragmatic wing, which includes former Vice President Joe Biden and several former governors and mayors who are considering running.

In Iowa, Warren said her childhood in Oklahoma shaped her populist economic views. She was the daughter of a janitor who lost work after a heart attack, forcing her mother to take a minimum wage job.

“That minimum wage job saved our house and it saved our family,” Warren said. “Today, a minimum wage job in America will not keep a momma and a baby out of poverty. That’s why I’m in this fight.”

‘JUST THE BEGINNING’

Local Democrats said they were anxious to start focusing on picking a challenger for Trump, although most said it was way too early for them to commit to a candidate.

“This is just the beginning, I’m excited to see it start,” said Lisa Koch, 48, an attorney from Council Bluffs who said she was a long-time fan of Warren’s but worried her gender, age or combative approach might turn off some voters.

Linda Drury, 62, of Holstein, Iowa, said she was impressed with Warren. She was afraid Warren might come off as angry, but “that’s not anger, that’s passion.”

A December Des Moines Register/CNN poll of likely 2020 Democratic caucus-goers in Iowa found Warren in fourth place with 8 percent support, trailing three candidates who have not yet entered the race - Biden at 32 percent, Sanders at 19 percent and former U.S. Representative Beto O’Rourke of Texas at 11 percent.

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That poll found 65 percent of likely caucus-goers viewed Warren favorably, and 20 percent saw her unfavorably.

Angela Nelson, 50, a special education teacher from Omaha, Nebraska, said she was concerned to see questions raised about Warren’s likeability amid comparisons to Hillary Clinton, the unsuccessful 2016 Democratic nominee.

“It bothers me that there is this test of likeability just because she is a woman,” Nelson said. “It’s time for our country to move beyond that.”

In Sioux City, Warren was asked by a member of the crowd about her controversial decision to take a DNA test to ease questions about her claims to Native American ancestry.

Trump frequently belittles Warren’s claims by calling her “Pocahantas,” but she faced criticism from fellow Democrats and Native Americans for taking the test.

“I am not a person of color. I am not a citizen of a tribe. Tribal citizenship is very different from ancestry. Tribes, and only tribes, determine tribal citizenship, and I respect that difference,” Warren said. “My decision was to put it all out there.”