Former U.S. Rep. Anthony Weiner leads City Council Speaker Christine Quinn in the race for New York City's Democratic mayoral nomination for the first time, snatching the frontrunner mantle as the contest heads into the final months before the primary, the latest survey from The Wall Street Journal-NBC New York-Marist showed.

Among registered Democrats, Mr. Weiner had 25% of the vote, compared with Ms. Quinn, who had 20%, marking her lowest level of support since polling of the race began. Trailing them were former Comptroller...