City Council Speaker Christine Quinn now leads the primary field with 27 percent of likely Democratic voters, with Public Advocate Bill de Blasio and former Comptroller Bill Thompson taking 21 percent and 20 percent, respectively. Weiner, a former congressman, has just 16 percent.
In the last Quinnipiac poll, taken just before he admitted to sending inappropriate messages and lewd photos to women as recently as last summer, Weiner had a 4-point lead over Quinn.
"With six weeks to go, anything can happen, but it looks like former Congressman Anthony Weiner may have sexted himself right out of the race for New York City mayor," said Maurice Carroll, director of the Quinnipiac University Polling Institute.
HuffPost Pollster's chart, which includes all publicly available polling, shows Weiner's rapid rise and fall since his entrance into the race. Meanwhile, de Blasio and Thompson have each seen their share of the vote increase in recent polls of likely voters. Simple averages of the polls show a roughly 5 point increase for Thompson and roughly 7 point increase for de Blasio.
The share of Democratic voters saying Weiner's history of sending of lewd photos is a legitimate issue in the race jumped 15 points, from 50 percent in the previous Quinnipiac poll to 65 percent in the new one. Forty percent now say that his behavior is a disqualifying factor, up from 23 percent just two weeks previously.
An NBC New York/Wall Street Journal/Marist poll taken last week, immediately after the latest revelations, yielded similar results, with Weiner slipping to third place and his unfavorable rating skyrocketing to 55 percent.
In the new Quinnipiac poll, a 53 percent majority said Weiner should drop out of the race. If he did choose to end his candidacy, Quinn would take 30 percent, with Thompson and de Blasio tied at 25 percent each.
Quinnipiac surveyed 446 likely Democratic voters by phone between July 24 and July 28.
Mark Blumenthal contributed reporting.