And David Oh, whose political obituary was written for most of the night, staged a late comeback in the final precincts to take a slim lead over Al Taubenberger, the party's mayoral candidate in 2007.
With a handful of precincts to be counted, about 140 votes separated the two, meaning days and possibly weeks until a winner is finally declared.
This is familiar territory for Oh, who led Kelly by seven votes on Election Day 2007, but lost by 122 votes after two weeks of tense counting and contesting of ballots.
"I'm optimistic, my numbers are good," Oh said at his campaign party Tuesday night. "It looks like a repeat, but my numbers are much better."
Even with O'Neill's victory, six new Council members will take office on Jan. 2, the largest spring-cleaning of Council since 1991, when Mayor Nutter was part of a class of seven new members.
How well Nutter works with this latest group of freshman could have a major impact on the success of his second term. He could pitch the newbies on ending the controversial DROP pension program and enacting a soda tax - ideas the current Council defeated without breaking a sweat.
"It's a substantial influx," said Nutter spokesman Mark McDonald. "I'm sure the mayor might hope that Council would rethink DROP."
Four District Council members with nearly a century of experience among them - Frank DiCicco, Joan Krajewski, Donna Reed Miller and Council President Anna C. Verna - are leaving at the end of the year.
Their replacements - all Democrats - won easily against no or nominal competition: Cindy Bass in the Eighth District, Bobby Henon in the Sixth District, Kenyatta Johnson in the Second District, and Mark Squilla in the First District.