Elizabeth Warren is running for the United States Senate for the right reason and with the right message.

In fact, her reason and her message are the same—a bit of political calculus that ought not be lost on Democrats who seem so frequently to stumble when it comes to aligning their ambitions and themes.

Warren wants to change the economic debate in a country where the poverty rate is rising, the middle-class is shrinking, the rich are getting dramatically richer and the corporations are writing the rules. In Warren’s words, working families have been “chipped at, hacked at, squeezed and hammered for a generation now, and I don’t think Washington gets it.”

“Washington is rigged for big corporations that hire armies of lobbyists,” she continued. “A big company like GE pays nothing in taxes and we’re asking college students to take on even more debt to get an education, we’re telling seniors they may have to learn to live on less. It isn’t right, and it’s the reason I’m running for the U.S. Senate.”

From a messaging standpoint, that is precisely the right place to begin a major 2012 campaign—with a bow to reality and an embrace of populism. And Warren, despite her Harvard Law background, has been around politics long enough to know where to deliver it.

She started Wednesday morning not in the halls of academies but at a Boston commuter station, where she greeted working men—in a campaign start that provided evidence that this, like all of Warren’s endeavors, will be a high-energy and people-powered project. And the nation’s most identifiable battler against the big banks and the Wall Street speculators was driving the message home. “The pressures on middle-class families are worse than ever, but it is the big corporations that get their way in Washington,” she said. “I want to change that.”

Before the finish of the day, Warren planned to take that message to the voters of New Bedford, Framingham, Worcester, Springfield, Lowell and Gloucester. That will help to position her for a Democratic primary race with several other contenders and, if she prevails as expected, a November 2012 face-off with Republican Senator Scott Brown.

Warren’s run is Massachusetts focused, by desire and necessity. She wants to take the seat held by former US Senator Edward Kennedy and to go to Washington as a Kennedy-style champion of economic and social justice.

It is that determination that makes this run more than a Massachusetts race, however.

It’s not just that a Warren candidacy could provide Democrats with a needed pick-up of a currently Republican-held seat—although that’s a big deal for the party, which faces a dismal electoral map in 2012. If the chief advocate for real banking reform and the development of a federal Consumer Financial Protection Bureau runs and defeats US Scott Brown, R-Massachusetts, she will instantly become an essential spokesperson for progressive values in national economic, regulatory and fiscal policy debates.

Put Warren next to stalwarts like Oregon Democrat Jeff Merkley, Minnesota Democrat Al Franken, Iowa Democrat Tom Harkin, California Democrat Barbara Boxer, a re-elected Vermont Independent Bernie Sanders,  a re-elected Ohio Democrat Sherrod Brown, as well as progressive candidates like Wisconsin Democrat Tammy Baldwin and Hawaiian Democrat Mazie Hirono—House members seeking open Senate seats—and you’ve got the makings of what Warren’s old friend Paul Wellstone always wanted: a Senate progressive caucus.

The calculus extends even further with Warren, however. Her ability to grab the spotlight and use it to push the discourse to the left on economic issues that the media so frequently neglect makes the prospect of her candidacy and Senate service potentially transformative for movements and a party that will—no matter what the 2012 presidential election results—begin pondering sometime next year the challenge of identifying leaders of the post-Obama era.

The Warren calculus has not been lost of progressives and progressive groups that have indicated a clear intention to help Warren—whose criticisms of Wall Street will require her to raise money from the grassroots—mount a winning campaign.

Even before Warren announced her candidacy, the Progressive Change Campaign Committee was promoting it, as Emily’s List mounted a “Tell Elizabeth Warren: We’ve Got Your Back!” campaign.

Of particular importance was the early decision of National Nurses United, a union that has made the shifting of the debate central to its 2012 political work, to take the unusual step of endorsing Warren before the professor formally announces her candidacy.

Technically, the 170,000-member union is endorsing Warren’s exploratory candidacy. But the move by the NNU left no doubt about the union’s sentiments. And it sends a powerful signal as regards the Senate race, as the endorsement by the national union follows a recommendation from its affiliate, the 23,000-member Massachusetts Nurses Association, which has also endorsed Warren.

“Her dedication to the nation’s middle class, which she has demonstrated through her work as a faithful consumer advocate both locally and nationally, reflects one of the MNA’s key goals: Restoring a basic standard of living for working people by creating financial remedies that hold Wall Street accountable while protecting those who live and work on Main Street USA,”  said MNA President Donna Kelly-Williams, RN. 

In preparing her candidacy, Warren went out of her way to meet with union activists across the state, and she made a profound impression on the nurses.

That’s important, as the Massachusetts Nurses Association maintains one of the most focused and effective political operations in the state, and it is especially strong in western Massachusetts, where Warren will need grassroots support to secure the Democratic nomination and election in November. In Massachusetts and other states, NNU works closely with Progressive Democrats of America, the activist group that has been in the forefront of fighting to push the Democratic Party toward a more militant stance when it comes to taxing the rich and defending Social Security, Medicare and Medicaid.

Warren will also benefit from NNU’s strong national political operation, which NNU executive director RoseAnn DeMoro said would focus particular attention on the Massachusetts campaign.

“Nurses have aligned with the public in seminal battles over the future of our communities throughout the country,” said DeMoro. “Nurses and patients together have shown the creativity and commitment to winning such efforts. We can take back our country from Wall Street. Elizabeth Warren will be a great ally.”