DES MOINES, IA - OCTOBER 19: U.S. Sen. Elizabeth Warren (D-MA) campaigns for U.S. Rep. Bruce Braley (D-IA) on October 19, 2014 in Des Moines, Iowa. Braley is in a tight race for a Senate seat against Republican challenger Joni Ernst. (Steve Pope/Getty Images)

Sen. Elizabeth Warren says she isn’t running for president. At this rate, however, she may have to.

The Massachusetts Democrat has become the brightest ideological and rhetorical light in a party whose prospects are dimmed by — to use a word Jimmy Carter never uttered — malaise. Her weekend swing through Colorado, Minnesota and Iowa to rally the faithful displayed something no other potential contender for the 2016 presidential nomination, including Hillary Clinton, seems able to present: a message.

“We can go through the list over and over, but at the end of every line is this: Republicans believe this country should work for those who are rich, those who are powerful, those who can hire armies of lobbyists and lawyers,” she said Friday in Englewood, Colo. “I will tell you we can whimper about it, we can whine about it or we can fight back. I’m here with [Sen.] Mark Udall so we can fight back.”

Warren was making her second visit to the state in two months because Udall’s reelection race against Republican Cory Gardner is what Dan Rather used to call “tight as a tick.” If Democrats are to keep their majority in the Senate, the party’s base must break with form and turn out in large numbers for a midterm election. Voters won’t do this unless somebody gives them a reason.

Warren may be that somebody. Her grand theme is economic inequality and her critique, both populist and progressive, includes a searing indictment of Wall Street. Liberals eat it up.

“The game is rigged, and the Republicans rigged it,” she said Saturday at Carleton College in Northfield, Minn. The line drew a huge ovation — as did mention of legislation she has sponsored to allow students to refinance their student loans.

Later, Sen. Al Franken (Minn.) — a rare Democratic incumbent who is expected to cruise to reelection next month — gave a heartfelt, if less-than-original, assessment of Warren’s performance: “She’s a rock star.”

In these appearances, Warren talks about comprehensive immigration reform, support for same-sex marriage, the need to raise the minimum wage, abortion rights and contraception — a list of red-button issues at which she jabs and pokes with enthusiasm.

The centerpiece, though, is her progressive analysis of how bad decisions in Washington have allowed powerful interests to re-engineer the financial system so that it serves the wealthy and well-connected, not the middle class.

On Sunday, Warren was in Des Moines campaigning for Democrat Bruce Braley, who faces Republican Joni Ernst in another of those tick-tight Senate races. It may be sheer coincidence that Warren chose the first-in-the-nation nominating caucus state to deliver what the Des Moines Register called a “passion-filled liberal stemwinder.”

There once was consensus on the need for government investment in areas such as education and infrastructure that produced long-term dividends, she said. “Here’s the amazing thing: It worked. It absolutely, positively worked.”

But starting in the 1980s, she said, Republicans took the country in a different direction, beginning with the decision to “fire the cops on Wall Street.”

“They called it deregulation,” Warren said, “but what it really meant was: Have at ’em, boys. They were saying, in effect, to the biggest financial institutions, any way you can trick or trap or fool anybody into signing anything, man, you can just rake in the profits.”

She went on to say that “Republicans, man, they ought to be wearing a T-shirt. . . . The T-shirt should say, ‘I got mine. The rest of you are on your own.’ ”

The core issue in all the Senate races, she said, is this: “Who does the government work for? Does it work just for millionaires, just for the billionaires, just for those who have armies of lobbyists and lawyers, or does it work for the people?”

So far this year, Warren has published a memoir, “A Fighting Chance,” that tells of her working-class roots, her family’s economic struggles, her rise to become a Harvard Law School professor and a U.S. senator, and, yes, her distant Native American ancestry. She has emerged as her party’s go-to speaker for connecting with young voters. She has honed a stump speech with a clear and focused message, a host of applause lines and a stirring call to action.

She’s not running for president apparently because everyone assumes the nomination is Clinton’s. But everyone was making that same assumption eight years ago, and we know what happened. If the choice is between inspiration and inevitability, Warren may be forced to change her plans.

Read more from Eugene Robinson’s archive, follow him on Twitter or subscribe to his updates on Facebook. You can also join him Tuesdays at 1 p.m. for a live Q&A.