Las Vegas (CNN) The 2020 Democratic contenders showed up in force at a labor forum on Saturday to outline their plans for raising wages and court the all-important constituency of labor as they seek foot soldiers for their campaigns.

It is a constituency that was once strongly behind Vermont Sen. Bernie Sanders, but in this crowded field of 2020 candidates, none of them are willing to cede that ground.

They came to this early caucus state Saturday armed with plans to fight for a $15 minimum wage, expand Medicare-for-All, unravel right-to-work laws, and to pressure corporate titans to pay more to Americans who are trying to patch together a living wage with two, and sometimes three, jobs.

Among the forum's questioners was Jennifer Berry, a McDonald's employee in Milwaukee who told California Sen. Kamala Harris on Saturday that she makes $9.90 an hour. With a two-week paycheck of $514, she said she must also rely on government assistance, including Medicaid, food share benefits and Wisconsin's housing program.

"In our America, nobody should have to work more than one job, so let's talk about our values," Harris said at the forum held by Service Employees International Union and the Center for American Progress Action Fund. "You can't go around talking about the golden arches as the symbol of the best of American when you are not conducting yourself in the best way in terms of supporting the working people of America."

Harris added that Americans "deserve to have a wage that allows them to keep up with the cost of living."

"We can talk about a minimum wage — of course, we need to fight for $15 — but really that's a minimum, that's a minimum standard of living," she said.

In her closing remarks about America being at an inflection point, she told the forum that "people are woke ... the challenge will be to harness that energy and to organize" to get people to the polls.

Sen. Elizabeth Warren spoke jokingly about billionaires not supporting her candidacy.

"Are you telling me that the billionaires are not in favor of my being President of the United States?" the Massachusetts Democrat said. "Damn, you just upset every plan I had -- I'm shocked. Gosh, I guess I might have to do it by getting out there, getting people organized, fighting for working people and persisting. We can win. We dream big, we fight hard. That's how we win, it's these folks."

Earlier in her speech, Warren talked about making government work for the people.

"How do we get the change to fight back?" she said. "There are a lot of places where we need to be in this fight. For openers, how about we do it through the Department of Labor? How about we say we want (a National Labor Relations Board) that's actually on the side of labor? And we want whenever employers interfere with the rights of workers to organize, to bargain collectively then we want an NLRB, we want a Department of Labor that comes in on the side of the workers and puts a stop to it."

Former Texas Congressman Beto O'Rourke was asked by moderator Steven Greenhouse how he would convince more conservative voters in his home state of Texas that a $15 an hour wage is a "good idea."

"When one job is enough; when you can focus on what you're doing at work and don't have to worry about the next job or the third job that you're going to in one 24-hour period, your productivity at work is going to be so much greater," O'Rourke said. "That business owner is going to get so much more out of that employee."

O'Rourke said that in Texas, nearly half of public school educators are working a second or third job "just to make ends meet."

"When everyone can just work that one job, they're going to be better at it and we will be better as a country," he said.

He cited his own campaign for US Senate in Texas last year as a reason why Democrats should not be afraid to take on right-to-work laws in states like Texas.

"We just ran a 254-county campaign in Texas — showed up in the most conservative, the most liberal, the smallest towns, the biggest of cities with this same message," O'Rourke said.

"Not only did we win more votes than any other Democrat in statewide Texas history, 500,000 of my fellow Texans who voted for Greg Abbott, a Republican tea party governor, also voted for us on the same ballot," O'Rourke added. "In other words, we do not have to allow our partisan differences to define us on issues of economic opportunity and equity — whether it's in our economy or education or in health care. So, we can take on this battle and win it."

Minnesota Sen. Amy Klobuchar also made a forceful case for a $15 per hour minimum wage, noting her own union roots and urging workers to fight against right-to-work laws not just through the courts.

"The best place we win is at the ballot box," she said.

She argued that the federal government should be doing more to negotiate lower drug prices through Medicare to bring down costs for everyone, as well as getting more generics on the market.

"You do it by actually bringing in drugs from less expensive countries like Canada that are safe, because I can see Canada from my porch in Minnesota, so I kind of like that," Klobuchar said to laughter.

Former Colorado Gov. John Hickenlooper, who outlined a new plan for raising the minimum wage on Saturday, said he believes Democrats can win back voters in Michigan, Wisconsin and Pennsylvania who voted for Donald Trump. The key, he said, is to "make sure that everybody has a ladder that they should be able to work their way up and find."

"Those voters are waiting for us to come make a pitch, and showing them that we'll give them a better job with a better income, a better future for their kids," Hickenlooper said.

The former Colorado governor outlined a plan Saturday to set a nationwide minimum wage floor at $15 per hour and permanently index the minimum wage to each area's cost of living.

Julián Castro, the former secretary of Housing and Urban Development, noted that he is supporting the unionization of his campaign, which follows in the footsteps of the Sanders campaign.

"I'm supporting the unionization of our campaign staff who are about to unionize and we're paying even our interns $15 an hour because we believe we ought to do the right thing," Castro said.