More than 125 candidates turned in paperwork to run for city office by Monday’s filing deadline, setting up a packed November ballot likely to leave every incumbent with at least one opponent.

The unusually crowded field is driven largely by the city’s move in 2015 to extend term limits, allowing officials to serve two four-year terms instead of three two-year terms, said Rice University political science Professor Bob Stein.

“It used to be that you just wouldn’t run against an incumbent. You would wait until they term-limited out,” Stein said. “Candidates are no longer getting the two-year pass.”

Thirteen candidates have filed to run for mayor, including incumbent Sylvester Turner, who is running for a second four-year term. Turner’s challengers include his 2015 runoff opponent, Bill King, lawyer and business owner Tony Buzbee, Councilman Dwight Boykins and former councilwoman Sue Lovell.

By Friday evening, the city’s legal department had approved applications from at least 97 candidates. Another 28 candidates had filed for office and were awaiting approval from the city attorney’s office, and an unknown additional number of candidates filed just before the 5 p.m. deadline.

Ten candidates were officially on the ballot for mayor, with three others awaiting legal department approval by the close of business Monday.

Early voting begins Oct. 21 and Election Day is Nov. 5.

All eight incumbent council members seeking re-election drew opponents, though the legal department had yet to approve applications from two candidates who filed to challenge District G Councilman Greg Travis.

Meanwhile, several council races drew large fields with candidates looking to replace outgoing council members seeking other offices or who cannot run again because of term limits.

Many of those races are likely to head to runoffs in December, with no candidates assured of getting 50 percent plus one vote, the total needed to win outright.

City Controller Chris Brown drew a last-minute challenge from former Harris County treasurer Orlando Sanchez, who launched his candidacy Monday on a platform of bringing more transparency to the office.

Sanchez, a Republican, said Brown did not conduct enough audits during his first term in office, while Brown defended himself as an “honest broker” of the city’s finances.

In District H, Councilwoman Karla Cisneros filed to run for a second term and will face former Houston planning commissioner Isabel Longoria and real estate agent Cynthia Reyes-Revilla, a member of several Near Northside neighborhood groups.

Also drawing multiple opponents was At-Large 1 Councilman Mike Knox, who will face Larry Blackmon, Georgia Provost and Raj Salhotra, and At-Large 3 Councilman Michael Kubosh, who is up against Janaeya Carmouche and Marcel McClinton.

At-Large 2 Councilman David Robinson, meanwhile, will face three opponents: Willie R. Davis, Emily Muñoz DeToto and Jim Honey.

A few council members drew just one opponent: District E Councilman Dave Martin, looking to retain the seat he won in a 2012 special election, is up against police officer Sam Cleveland, and District I Councilman Robert Gallegos will face Richard “Rick” Gonzales in his bid for a final four-year term.

Open seats proved the most popular.

Among the city council seats with the most candidates is District C, which has drawn 13 people vying to succeed Mayor Pro Tem Ellen Cohen in the seat representing the Heights, Oak Forest, Meyerland and Montrose. The candidates include civil rights lawyer Abbie Kamin and longtime activist Shelley Kennedy.

Two candidates who initially intended to run for District C — Anthony Dolcefino and Nick Hellyar — decided instead to run for the At-Large 4 seat left open by Councilwoman Amanda Edwards, who is running for U.S. Senate instead of seeking re-election.

Eight candidates are running for Edwards’ seat, including business owner and former congressional candidate Letitia Plummer.

Other open seats include District B, being vacated by term-limited Councilman Jerry Davis, and Boykins’ District D. Twelve candidates have filed for District B, while 10 are seeking the District D seat.

A handful of additional candidates had filed applications for the seats and were awaiting confirmation from the city.

Other popular open seats include term-limited Councilman Mike Laster’s District J seat, which has drawn at least six candidates, as well as the At-Large 5 seat being vacated by Jack Christie. The candidates include Sallie Alcorn, Catherine Flowers, Marvin McNeese, Sonia Rivera and Ashton Woods.

Three candidates filed and were approved by Friday for Councilman Steve Le’s District F seat, while four others had filed without yet receiving approval from the legal department. Le announced in July he would not seek re-election.

Five candidates filed for the District A seat held by term-limited Councilwoman Brenda Stardig, including Stardig’s chief of staff, Amy Peck, and 2015 District A candidate Iesheia Ayers-Wilson.

Also on the November ballot are four races for the Houston ISD board of trustees.

Two incumbents filed paperwork Monday to seek re-election and will each face a single challenger, while several candidates will jostle to fill two other open seats on a school board that could soon be stripped of power.

HISD Board President Diana Dávila and Trustee Sergio Lira made their re-election runs official hours before Monday's afternoon deadline, while trustees Jolanda Jones and Rhonda Skillern-Jones will not seek another term.

HISD will continue with elections despite the looming possibility that Texas Education Commissioner Mike Morath will remove all powers from elected trustees and appoint a board of managers comprised of local leaders, the result of chronic low academic performance at Wheatley High School.

Reporters Jacob Carpenter and Rob Downen contributed to this report.

jasper.scherer@chron.com