The Quinnipiac University Poll (done between September 15th and 18th of 891 likely voters -- with a 3.3 point margin of error) verifies that huge lead by de Blasio. Quinnipiac has him with a 41 point lead over Lhota and a 64 point lead over Carrion. I have included the demographic breakdown for the Quinnipiac poll to show that deBlasio leads by a large margin with every race, income level, gender, educational level and age group.
Lhota (and Carrion) have a very large mountain to climb just to get back in this race.