Sen. Bernie Sanders fired up big crowds in St. Paul and Duluth on Tuesday, trying to keep momentum building for his surging Democratic campaign just days from when the first votes of the presidential race are cast.

More than 14,000 people came to St. Paul's RiverCentre — a third of them in an overflow crowd — for the Vermont senator's evening speech, and earlier, about 6,000 people packed his afternoon rally at the Duluth Entertainment Convention Center.

In both cities, Sanders spoke in typically fiery fashion on his themes of reducing income inequality, breaking the influence of big money in politics and reforming the criminal justice system.

"You, and millions of other people, need to come together," Sanders said in Duluth, adding that what he advocates is no less than a political revolution. "You need to say loud and clear that when so many men and women fought and died to save our country, that we the people are going to have a government that represents us, not just a handful of billionaires."

In St. Paul, he said that no president "can effectively address the crisis facing our country unless there is a political revolution." The crowd cheered when he attacked the campaign finance system as corrupt and the criminal justice system as broken, and booed when he singled out Wal-Mart for not paying its workers enough and railed against Wall Street, corporate America, the corporate media and the Koch brothers.

"Today in America, we have a rigged economy," Sanders said. "People are sick and tired of working long hours for lower wages." He vowed to make paid family medical leave and a $15 minimum wage a reality.

"Some kid in Minneapolis gets arrested for selling marijuana, that kid gets a police record," he said, as the crowd booed. But a Wall Street executive whose behavior brought the economy into the worst recession since the 1930s gets nothing, he continued, adding, "...Wall Street's greed is destroying our economy."

One of the loudest cheers came for Sanders' call for "major reform in the way police departments function." While saying that he believes most police officers act responsibly, he said it was not acceptable to see unarmed people, particularly Latinos and African-Americans, "killed in cold blood."

"When a police officer breaks the law, that officer must be held accountable," he said.

Shannon Chapa, 39, said she was skeptical of him at first, but "I think he really listens to those of us who aren't the 1 percent."

Ken Brown, 72, came from Menomonie, Wis., to see Sanders. "Hillary [Clinton] hasn't got enough strength to withstand the competition," he said.

Waiting for Sanders, who spoke first to the overflow crowd, they heard from Farhiya Ali, a Hamline University student, and U.S. Rep. Keith Ellison, D-Minn. Ali drew cheers when she called for addressing institutional racism and the way cities are policed — and when she made a dig at Republican candidate Donald Trump by saying Sanders would bring change "rather than scapegoating Latinos or Muslims."

Rising influence

Initially viewed as a long shot due to his quirky style and self-professed socialism, Sanders, 74, has recently risen to near equal or even ahead of Clinton in a handful of polls of Democratic voters. The biggest test of his underdog bid comes Monday, when Iowans gather for their first-in-the-nation caucuses.

Sanders started Tuesday in Des Moines at a rally with a United Steelworkers local that's backing his bid. How he fares in Iowa will go a long way in determining whether he can keep up a fight against Clinton. Sanders told reporters at the Des Moines event that big turnout is key to his success.

Minnesota holds its own caucuses on March 1. A Star Tribune Minnesota Poll last week showed Clinton leading Sanders 59 percent to 25 percent among Democratic-leaning voters in the state. Sanders would beat Republican Donald Trump in a head-to-head matchup, the poll found. Sanders drew his strongest support in Minneapolis and St. Paul, but he also beat Trump in outstate Minnesota.

The Washington Post reported Tuesday that Sanders would hold a private meeting Wednesday with President Obama in the Oval Office. No agenda was announced, but it comes on the heels of Obama recently praising Clinton. The president has stressed, however, that he intends to remain neutral in the race for the Democratic nomination.

Resonating with the young

The size of the crowds showed how Sanders' populist, anti-establishment message is resonating. The crowds were particularly well-stocked with young people.

"He has the people's best interests in mind and his heart is in the right place," said Paige Melius, a 23-year-old environmental sciences major at the University of Minnesota Duluth at the afternoon rally. Asked if she'd vote for Clinton should she become the Democratic nominee, Melius said she'd be more inclined to write in Sanders.

In his Duluth speech, Sanders ripped into perceptions that Clinton would be a better candidate for Democrats. He also said: "There's nothing more in this life that I would look forward to than running against Donald Trump."

Staff writer J. Patrick Coolican in Des Moines contributed to this story. 612-673-4210 651-925-5049