In Democratic circles, disappointment in the promise of the Obama presidency and unease over a possible restoration of the Clintons have made the senator, who was sworn in just 10 months ago, the object of huge interest and the avatar of a newly assertive, fervently populist left eager for a more confrontational approach to politics.

Ms. Warren, a Massachusetts Democrat, said in an interview that she was not interested in seeking the presidency. And despite talk of a draft movement among some activists, it is difficult to imagine her taking on former Secretary of State Hillary Rodham Clinton.

But in seizing on issues animating her party’s base — the influence of big banks, soaring student loan debt and the widening gulf between the wealthy and the working class — Ms. Warren is challenging the centrist economic approach that has been the de facto Democratic policy since President Bill Clinton and his fellow moderates took control of the party two decades ago.

“She is reshaping the Democratic Party and leading its charge toward a more economic populist orientation,” said Markos Moulitsas, the publisher of Daily Kos, a leading liberal blog…

The ascendant power of Ms. Warren and her fellow populists is best captured by their torpedoing this month of Lawrence H. Summers, Mr. Clinton’s treasury secretary, who was blocked before President Obama could even nominate him to lead the Federal Reserve. And the victory of Bill de Blasio, who hammered home a message of income inequality, in New York City’s Democratic primary for mayor has given the party’s progressive base even more confidence.