Democrats searching for sparks of progressive energy see the ascent of Benjamin T. Jealous in Maryland as an encouraging electoral sign.

Mr. Jealous, the former head of the N.A.A.C.P., is an ally of Senator Bernie Sanders who had campaigned for governor on single-payer health care and tuition-free college, among other Sanders-like positions. On Tuesday, he emerged from a crowded Democratic primary field by beating a more moderate candidate, Rushern Baker, by more than 10 percentage points.

Along with the seismic triumph of Alexandria Ocasio-Cortez in New York, his victory signaled enthusiasm behind Democratic candidates who are further to the left than many incumbents and added to the debate about how their positions will affect the party’s chances in general elections.

Whatever Mr. Jealous’s odds of victory are in November, at the moment he’s widely seen as an underdog to the popular incumbent governor, Larry Hogan, a Republican who has enjoyed approval ratings in the 60s and topped out at 71 in January. A Washington Post poll from May 29 to June 3 had Mr. Hogan ahead of Mr. Jealous in a hypothetical election by 12 points.