City Council Speaker Christine Quinn now has 25 percent support among Democratic primary voters compared with 16 percent for Weiner, according to the poll by NBC 4 New York, The Wall Street Journal and the Marist Institute for Public Opinion.
At a Tuesday press conference addressing the sexting scandal, Weiner's wife, longtime Hillary Clinton aide Huma Abedin, stood by her husband, saying "I forgive him."
"I made the decision that it was worth staying in this marriage, and that was a decision I made for me, for our son, and for our family," Abedin said. "Anthony has made some horrible mistakes both before he resigned from Congress and after, but I do very strongly believe that that is between us and our marriage."
A month ago, Weiner led Quinn by five points. More than half of Democratic voters, 55 percent, have an unfavorable opinion of Weiner compared with 30 percent who view him favorably. Last month, 52 percent viewed Weiner favorably.
In the wake of the poll results, Weiner revealed Thursday that he had online sexual relationships with at least three women after he resigned from Congress, saying "there were a few," but "not dozens and dozens."
Voters are divided over whether he should drop out -- 43 percent said he should quit the race and 47 percent said he should stay in.
Weiner is back on the campaign trail today, pressing forward despite calls from rivals and two of the city's largest newspapers to pull out of the race.
As to whether Abedin's public forgiveness will help him among voters, nearly three quarters of respondents said her support will have no impact on their vote.