Tweeting that “America needs a political revolution,” Vermont Sen. Bernie Sanders threw himself Thursday into the race for the Democratic nomination for the presidency.

Sanders is in many ways the mirror image of Hillary Clinton, the favored candidate in the race. She has universal name recognition, unlimited funds, and a campaign operation rife with experienced political pros. He is not widely known, has little money, and has never run a national campaign. But in a populist moment, he is the real deal – a full-throated, unabashed, independent, uncorrupted, straight-talking populist. And that is a big deal.

Sanders will focus his campaign on the great challenges facing the country: a politics corrupted by big money, and an economy where the rules have been rigged by the few to benefit the few. That reality won’t be changed by politics as usual, where the viability of a candidate is measured by how much money he or she can amass in the backroom “money primary,” and the message of a candidate is judged by its poll-tested ability to appeal to voters without alarming donors. It will take an independent political movement to change our course – and Sanders will run as its Tom Paine, summoning Americans to save their democracy.

Sanders has already released a 12-point Economic Agenda for America. He has been a leader in what is increasingly a consensus agenda for Democrats: an increase in the minimum wage, paid sick days, paid vacation, pay equity, affordable child care.

But Sanders’ agenda is far bolder. It addresses the structures that are geared to generate extreme inequality. Since 1978, CEOs have increased their own pay by almost 1,000 percent, while the wages of 90 percent of Americans have lost ground. As Sanders says, that can occur only if the rules are systematically rigged to favor the few.

So Sanders calls for an end to the corporate-defined trade and tax policies that have racked up unprecedented and ruinous trade deficits while shipping good jobs abroad. He is a leader in the effort to stop fast track and the Trans-Pacific Partnership, which is supported by the Democratic president, the Republican congressional leadership and the business lobby.

He calls for breaking up the big banks, and making Wall Street serve rather than savage Main Street. The big banks are more concentrated than ever. Too big to fail, too big to jail, they are too big to exist. His leading donors are unions, not Wall Street bankers.

He calls for expanding, not cutting back basic security programs for America. He would lift the cap on Social Security payroll taxes to expand benefits to address the looming retirement crisis. He would move to a national health care plan – Medicare for all – that takes on the insurance and drug lobbies and makes health care a right. He would provide two years of debt-free college or advanced training for every student willing to earn it.

He calls for empowering workers, protecting the right to organize, fostering worker-owned cooperatives, while curbing the perversities of CEO compensation. This would help ensure that workers share in the profits and productivity that they help to generate.

He calls for fair taxes on the rich and corporations to invest in rebuilding our decrepit infrastructure and in renewable energy, creating jobs while leading the global effort to address catastrophic climate change.

He challenges the bipartisan consensus that America must police the globe, arguing that endless war will waste precious lives and sap our resources. He was against the Iraq intervention from the first lie.

And of course, he opposes big money in politics, and will drive reforms to clean up Washington’s corrupted revolving door lobby culture.

Many pundits suggest that there is little difference among Democrats. All are social liberals. All have become more “populist” in line with the times. But the real question is who is prepared to take on the entrenched structures that generate inequality and drive down wages. Sanders will put that question to voters and to his rivals.

A Test of Populist Energy

Sanders’ candidacy is less a test of the power of the populist message – its reach is apparent as even Republicans struggle to address economic inequality – than a test of populist energy and independence.

He starts with little money and less staff. He will camp out in Iowa and New Hampshire, raise money over the Web, largely in small donations. His message will be powerful in retail politics – house parties, rallies, town meetings and debates. The biggest obstacle is less to convince voters that he’s right than to convince them that he’s a serious candidate, worth supporting. He has to find ways to get a hearing. And he has to find ways to overcome understandable cynicism.

That is the challenge to the emerging populist movements. Will they be willing to support a long-shot candidate who is carrying their message? Or will they be fearful of alienating the powers that be, isolating themselves politically and losing their “access.”

For example, the brilliant Run Warren Run movement is headed to a moment of truth. It has built, by all accounts, the best operation on the ground in Iowa of any campaign. But the candidate of its dreams, Sen. Elizabeth Warren, remains clear that she has no intention of running. Their best hope now to get her to change her mind is to support Sanders big time, and show the power of his message in Iowa and New Hampshire. Sanders might be the Gene McCarthy to her Bobby Kennedy, opening the space for her to come in. He might also simply take her place as their champion. But that requires going full out for Sanders and against Hillary and other potential contenders. Are they independent enough to do that?

Similarly, the money-in-politics groups have shown that their issue is an increasingly potent one. Now they have a candidate who can credibly put the issue at the center of his campaign. Are they independent enough to recognize that, magnify his message, and rally to his side?

Similarly, labor leaders understand that they cannot survive with business as usual. AFL-CIO President Richard Trumka argues that to get labor’s support, candidates must step up:

“We want action. We want big ideas, and we want structural change. We want Raising Wages. That also means no candidate can be all things to all people and still meet this standard. Standing with working people once in a while won’t work. Candidates can’t hedge bets any longer….

Sanders meets that standard and puts labor’s challenge to the test.

The Sanders Effect

How Sanders will fare remains to be seen. The obstacles are forbidding. Clinton is a powerful and popular opponent. Sanders needs enough money to create the presence that will enable voters to see him as a serious choice. He has to rally activists to supply the energy that can supplant expensive paid field operations. Coming from Vermont, he has limited connections with the minority voters who are critical to the Democratic coalition. He has to find a way not only to get his message heard, but also how to get around the established gatekeepers in the black and Latino communities who will be lined up with Clinton. He has to exceed expectations in Iowa and New Hampshire, and see if he captures the public’s attention.

Many pundits and activists argue he’ll be good for Clinton. Like a batting practice pitcher, he’ll help her hone her stroke for the general election, and move her to the left. This is insulting to both Sanders and Clinton. She’s an experienced and sophisticated leader and candidate. She’s been moving to the left in part because the problems of the country leave little choice, and in part because that is where the voters are. She’s been in presidential politics for over a quarter century. She doesn’t need a practice run.

And win or lose, Sanders’ campaign will have far greater importance than serving as Clinton’s trainer. His message will reach millions, helping to reinforce the central realization that the rules have been rigged against them. He will powerfully attack Republicans for both their fawning billionaires competition and their reactionary economics. He’ll attract new energy, young organizers and activists who will gain experience and grow. New talented leaders will emerge through the campaign, using it to widen their own base and establish their own credentials. Out of the Jesse Jackson campaign in 1988, for example, came Paul Wellstone, who ran his operation in Minnesota and David Dinkins who put together the winning coalition in New York City, and many more.

Running for president against the Clinton operation, with little money and limited name recognition, risks embarrassment and reputation. Sanders has decided that the stakes are high enough and it is time to take that risk. Whether you support him or not, don’t discount him. He’s the real deal and this is a big deal.