On a two-day tour of Nebraska and Iowa — more than 1,200 miles from the New York City Hall where he has presided for 15 months — Mr. de Blasio is seeking to transcend his relative obscurity and jump-start a countrywide movement to promote liberal policies like raising taxes on the rich.
Already, the mayor’s effort is drawing scrutiny. His refusal this week to endorse the presidential candidacy of Hillary Rodham Clinton, his former boss, spurred criticism from more centrist Democrats, who questioned whether the mayor had earned the credibility to drive an insurgency within his party.
Mr. de Blasio’s aides did not anticipate the fierceness of the backlash to his comments about Mrs. Clinton, according to several people familiar with their thinking, but the episode underscored the notion that he could be positioned as the standard-bearer for the American left.
That is an image the mayor is keen to cultivate. A profile in Rolling Stone magazine is in the works. A forum for presidential candidates is being planned. The mayor will travel to Milwaukee and Washington this spring, and his aides are eyeing a West Coast trip to confer with liberal leaders in California.
First, however, the cerebral Mr. de Blasio will have to overcome a less lofty problem: basic name recognition. In Iowa, where he will appear on Thursday with former Senator Tom Harkin, political strategists said he remained unknown.
