Democrat Bill de Blasio became his party's presumptive nominee in the race for New York City mayor on Monday, after his chief rival Bill Thompson conceded the primary and Gov. Andrew Cuomo gave his endorsement for the general election.

Mr. de Blasio, who has campaigned as an unabashed liberal looking to break from nearly 12 years of Mayor Michael Bloomberg, also is expected to win the endorsements soon of other major New York Democrats, including U.S. Sens. Charles Schumer and Kirsten Gillibrand.

Mr. de Blasio will face Republican nominee Joe Lhota, who once ran the state agency overseeing the region's mass-transit system, as well as several third-party candidates in the November election.