The former governor had jumped into the race late -- just five days before the deadline to submit signatures for his candidacy. He challenged Stringer, who had until then been running unopposed for the comptroller job.
"I was surprised that he got in, but it was masterful that he got in late so there could be no opposition and he caught Stringer unawares," said Hank Sheinkopf, a Democratic strategist who worked with Spitzer in his Attorney General campaign. "He expected to walk into this with no opposition whatsoever, which is most unusual in New York City."
And at one point it looked like Spitzer could go all the way, with polls showing him ahead of his Stringer by a nearly 20-point margin.
Spitzer had all but acknowledged that he sought the lower office as a signal of repentance for his past misdeeds -- and an opportunity for political rebirth.
In the end, Spitzer appeared the repentant workhorse to Weiner's show horse. As Spitzer rose, Weiner fell.
"What has surprised me is that this is the greatest circus New York has ever seen," said Sheinkopf, who is a consultant for another mayoral candidate, Bill Thompson. "Better than the ones in Madison Square Garden."
ABC News' Ben Waldron and The Associated Press contributed to this report.