Mayor Bill de Blasio should be at the peak of his powers. Crime is down. The economy is up. He has scared away his most serious possible challengers this election year.

But in two dozen interviews, with Mr. de Blasio’s own aides and allies, city officials, leading political strategists and veterans of New York politics, there was near-universal agreement that though Mr. de Blasio is on more of a glide path to re-election in New York City than any mayor in a generation, he is still struggling to project his political voice in a job that has long produced towering national figures.

He has spent the second half of his first term bogged down in internecine fights with the governor, battling with and lecturing the press, and fending off federal and state pay-to-play investigations involving his donors. His ventures to expand his influence beyond New York City have mostly flopped: An effort to organize a presidential forum in Iowa collapsed; his nonprofit to pursue a national progressive agenda is in mothballs; he’s been passed over for prominent national speaking roles.

If Rudolph W. Giuliani ended up as “America’s mayor” and Michael R. Bloomberg exited office with lofty talk of being “mayor of the world,” Mr. de Blasio’s moniker, as he heads toward the Democratic primary on Tuesday, is still very much to be determined.