But Mr. de Blasio’s party affiliation is not his only strength, the poll found. His campaign themes emphasizing income inequality, improving public education and creating housing seem to be resonating. He continues to enjoy ratings that any elected official would envy, with 62 percent of likely voters viewing him favorably, and only 22 percent unfavorably. Nearly half of likely voters said Mr. de Blasio’s greatest strength was his ability to understand the needs and problems of people like them. And more than half said they thought that he would bring about change that would make the city better, while only 13 percent thought that change wrought by a de Blasio administration would make the city worse.

As is always the case for any election, an unexpected last-minute event or revelation could alter the dynamic, shift the momentum or dampen turnout. But nothing Mr. Lhota has done, including television commercials and a strong performance in last week’s debate, has improved his standing with voters thus far. In fact, the poll suggested that the more voters get to know Mr. Lhota, the less they like him: his unfavorable rating has climbed at a faster rate than his favorable rating since the last Times/Siena poll in early October.

There is also an apparent enthusiasm gap: most Democratic voters say the race for mayor has been interesting, while most Republican voters say it has been dull.

Mr. de Blasio won the Democratic primary by running as the most liberal of the major candidates in the field; he has proposed raising taxes on high-income New Yorkers and has supported greater oversight of the Police Department. Nonetheless, one in five Republicans are supporting him for mayor, suggesting in follow-up interviews that they are looking for change after eight years with Rudolph W. Giuliani as mayor followed by 12 years with Mayor Michael R. Bloomberg.

“I think de Blasio’s policies will be a change for the better from the Bloomberg era,” said Duane Dowden, a 33-year-old Brooklyn Republican who is a student in social work. Oswald Ramotar, a 51-year-old Queens Republican, agreed, saying, “I’m voting for de Blasio because I think he would bring better changes than Lhota would, like creating more jobs.” And Erick Washington, a 59-year-old Brooklyn Republican, said, “I’m not voting for Lhota because I feel that would be the same as voting for the Giuliani administration.”