On August 4 I tweeted that “Smart money is on de Blasio edging out [Bill] Thompson” for the second spot on the runoff. I followed that up by noting that Christine Quinn’s trajectory was troubling; it is not a good sign for a runoff if you are heading in the wrong direction. Both statements proved prescient as de Blasio was fourth in the polls on August 4 and is the current heavy favorite to be the next mayor of New York City. Meanwhile Quinn’s downward trajectory may push her out of a potential runoff, or even ameliorate the need for a runoff. But, Twitter does lead a little too much to the imagination, so here are some more details on the New York City mayoral contest.

The election in New York City is, potentially, a three step process. First, both parties have a primary on September 10. Second, if no candidate receives over 40% of the vote in the primary, there is a runoff between the top two candidates on October 1. Third, there is an election between the Democratic and Republican candidate on Tuesday, November 5.

Through the end of July Quinn and Anthony Weiner were trading spots on the top of the polls with de Blasio and Thompson battling it out for third and fourth. The New York Times poll that was in the field from August 2-7 showed the completion of Weiner’s fall to nearly single digits, but Quinn still had a lead and there were a huge amount of undecided voters; de Blasio was third with 14% and Thompson second with 16%. After that, August saw a string of six straight polls with de Blasio leading, finally blowing past 40% with the latest Quinnipiac poll that was in the field from August 28-September 1.

Meanwhile, Quinn continued to plateau through July with a string of polls with her leading, but always in the 22% to 32% range and no upward trajectory. As the frontrunner, this was troubling, because she has a lot of time to make her case to the Democratic electorate. Since then she has shown a consistent downward trajectory with the last three polls putting her below 20% and, crucially, below Thompson.

The smart money I was referring to on August 4 was the bookies like Paddy Power, Stan James and few other others; but, it was not as easy picking out the best odds. First, Quinn had the best odds of all, so she was still the favorite to get one of two spots in the potential run. Second, de Blasio had slightly more favorable odds than Thompson. The polls showed them nearly tied, but the betters favored de Blasio. Thus, the smart money had de Blasio pulling ahead of Thompson. Third, with Quinn still dominating the polls the bookies had no reason to push Quinn down below de Balsio and Thompson; it was still safe money to assume she had a higher probability than either de Blasio or Thompson. But, did she have a higher probability than the ultimate winner of the "not-Quinn" fight between de Blasio and Thompson; in my reading of the data, no.

The likely Republican candidate, Joe Lhota, is trailing any Democratic candidate by a wide margin. After five terms of Republican mayors, the Big Apple looks poised to put a Democrat back in Gracie Mansion and it is about 60-65% Bill de Blasio will be the next mayor of NYC.1

Then again, my friend Andrew Gelman of Columbia has a timely reminder for us in his blog: primary elections are hard to predict.

1Technically Mr. Bloomberg did not bother to occupy mansion and Mr. Giuliani was barred from living there, with his girlfriend, towards the end of his term …