On the afternoon of July 18, in remarks from the Rose Garden amid the bruising showdown with congressional Republicans over the debt ceiling, President Obama made what the White House billed as a simple “personnel announcement.” In a brief speech, the president announced that he was nominating Richard Cordray, the former attorney general of Ohio, to head the Consumer Financial Protection Bureau, the new government agency set up to protect consumers from abusive lending practices. In his remarks he described the agency, part of the massive 2010 Dodd-Frank Wall Street Reform and Consumer Protection Act, as creating “the strongest consumer protections in history,” set up “so ordinary people were dealt with fairly.” After which he turned to thank the woman standing to his right, Elizabeth Warren.

A Harvard law professor, one of the nation’s leading bankruptcy experts and consumer advocates, the 62-year-old Warren had come up with the idea for the agency in 2007. She had advised the Obama administration on its creation in the aftermath of the 2008 financial collapse and helped to push it through Congress. Warren had also spent the last 10 months working tirelessly to build the agency from scratch—hiring its staff of 500, including Richard Cordray, organizing its management structure, and getting the C.F.P.B. up and running for its opening on July 21.

As she crisscrossed the country, spreading the word about the C.F.P.B., Warren became a familiar face to many, especially to those who had seen her on television—on CNBC, Real Time with Bill Maher, and The Daily Show with Jon Stewart. She had gained millions of supporters. With her passionate defense of America’s beleaguered middle class, under assault today from seemingly every direction, she had become like a modern-day Mr. Smith, giving voice to regular citizens astonished at the failure of Washington to protect Main Street—and what increasingly appeared to be its abandonment of middle-class Am...