New York City mayoral candidate Anthony Weiner admitted Thursday to having online sexual relationships with as many as three women after he resigned from Congress, while a new poll showed his support has eroded following the latest revelations this week.

Weiner stammered and hesitated as reporters pressed him for the number of women he messaged since the 2011 resignation, saying at one point "there were a few," then promising "it's not dozens and dozens." He tried to duck the question by saying he wasn't sure what some would consider an inappropriate relationship.

He finally admitted "I don't believe I had any more than three," in addition to the six he had already admitted to in 2011. Weiner said Thursday he was in therapy and does not consider the problem an addiction.

"I sought help, I got help, I sought the help of my wife, and like problems that people have, this one, thankfully, is behind me," he said.

The new NBC 4 New York/Wall Street Journal/Marist Poll released Thursday found Weiner's favorability rating among registered Democrats has tanked since June, from 52 percent to 30 percent, according to the poll conducted Wednesday. Over that same period, the percentage of Democrats who said they had an unfavorable impression of Weiner spiked from 36 to 55.

His lead over City Council Speaker Christine Quinn has also evaporated; 25 percent of Democrats said they'd now vote for her in the Sept. 10 Democratic primary, and 16 percent said they'd back Weiner. A poll conducted last month had Weiner leading Quinn 25 percent to 20 percent.

"These new revelations have cost Anthony Weiner the lead in the Democratic field," said Lee Miringoff, director of the Marist College Institute for Public Opinion. "His negatives are at an all-time high."

The reversal puts Weiner among a pack of contenders for the second spot in a runoff, which is looking increasingly likely, as no single candidate appears able to break the 40 percent mark. Weiner is now in a statistical tie with Public Advocate Bill de Blasio and former Comptroller Bill Thompson, who are both at 14 percent.

In the back of the pack are current Comptroller John Liu at 7 percent, Bronx pastor Erick Salgado at 2 percent and former City Councilman Sal Albanese at 1 percent.

The poll questioned 551 registered Democrats, with a plus or minus 4 percentage point margin of error. See the full poll here.

A significant number of Democrats, 19 percent, remain undecided.

The poll focused on the Weiner revelations, which centered on a woman coming forward this week to say she had an online sexual relationship with Weiner, who used the name Carlos Danger, a year after he resigned from Congress.

The woman, Sydney Leathers, came forward Thursday and told "Inside Edition" she last heard from Weiner a few months ago, when he asked her to delete their chats.

"Obviously I knew he wanted me to erase any evidence of our conversations because that was around the time I knew that he was going to run for mayor," she said.

Last month's poll showed 59 percent of Democrats saying Weiner deserved another chance. After this week's news, that number dropped to 47 percent, with 45 percent saying he didn't have the character to be mayor.

Weiner's campaign did not immediately comment.

Democrats were split on whether Weiner should drop out of the race, as several candidates and newspapers have demanded. The poll found 43 percent of Democrats said he should quit, and 47 percent said he should keep running, numbers within the 4.2 percentage point margin of error.

Weiner has vowed not to drop out.

The poll also found that 46 percent of Democrats said the sexting scandal mattered a great deal or a good amount to them when it came to deciding who to support. More than a third -- 35 percent -- said the scandal didn't matter to them at all.

After news reports of the latest affair surfaced on Tuesday, Weiner and his wife, Huma Abedin, held a press conference where they said they were trying to move on from a painful time in their marriage.

Abedin spoke for the first time publicly about her husband's online activities, saying he had "made some horrible mistakes, both before he resigned form Congress, and after. But I do very strongly believe that that is between us and our marriage."

When respondents were asked if his wife's support makes a difference in whether they trust Weiner as a candidate, an overwhelming 73 percent said it makes no difference; 15 percent said it makes them more likely to trust him and 12 percent said less likely.

The day after the press conference, Weiner told supporters in an email that he won't abandon his campaign for mayor and promised the scandalous behavior is in the past.

"These things I did, as you have read in the papers, didn't happen once. It was a terrible mistake that I unfortunately returned to during a rough time in our marriage," he wrote.

While Weiner struggles in the mayoral race, comptroller candidate Eliot Spitzer does not seem hindered by his own sex scandal -- revelations of his involvement in a prostitution ring -- which forced him to resign as governor in 2008.

This week's poll showed that Spitzer has widened his Democratic primary lead over Manhattan Borough President Scott Stringer.

Spitzer leads Stringer 49 percent to 32 percent, the poll found. An earlier poll had Spitzer leading 42 percent to 33 percent.

"These are two campaigns headed in different directions," Miringoff said. "Spitzer is doing well. And Weiner is floundering."