A majority of Seoul voters support Mayor Park Won-soon, who is standing again as candidate for the main opposition New Politics Alliance for Democracy, over the elderly establishment challenger from the Saenuri Party.
A straw poll by Media Research for the Chosun Ilbo on Monday and Tuesday gave Park 53.3 percent support over Hyundai scion Chung Mong-joon's 32.9 percent.
The poll was carried out right after the two main parties picked their Seoul mayoral candidates.
In an earlier poll on April 11-12, Chung beat Park by three percentage points, well within the margin of error, with 48.5 percent to 45.5 percent.
But the tables have been turned within just in a month, with Park now having a whopping 20.4-point lead.
Noncommittal responses more than doubled from six percent to 13.8 percent.
The poll of 537 adults in Seoul was conducted through random digit dialing.