The filing deadline was Monday, Oct. 26. Among the candidates who submitted petitions that day were retiring Illinois Comptroller Susana Mendoza, cardiologist Lisa Nee, Cook County Board of Review Commissioner George Cardenas and Cook County Treasurer Maria Pappas. Other final-day filers included attorney William Quinlan, businessman Joe Holberg, conservative Danielle Carter-Walters and former real estate developer Zoe Ma.

Five candidates filed on the first day of the filing period: Illinois Secretary of State Alexi Giannoulias, lobbyist John Kelly, former Chicago Housing Authority Chair Matthew Brewer, U.S. Rep. Mike Quigley and businessman Willie Wilson. Johnson filed on Friday and reported submitting 33,000 signatures.

Candidates must have at least 12,500 valid signatures to stay on the ballot. The challenge period begins Tuesday, Oct. 27, and closes Nov. 2. Election officials are scheduled to complete review of challenges by Dec. 17, when the final mayoral ballot is to be certified.

Several candidates reported submitting totals well above the minimum, though those counts have not yet been validated. Mendoza reported 26,000 signatures; Nee, 31,000; and Cardenas, 31,500. Pappas said she submitted slightly fewer than 40,000. Holberg reported 32,000, Carter-Walters 13,000 and Ma 17,000.

The petition review could become an early test of campaign resources and organization. Giannoulias’ campaign manager, Hana Jubeh, said the campaign plans to examine every candidate’s filings. Giannoulias has a reported $19.3 million campaign fund, giving him substantial resources to pursue challenges.

Wilson also expects scrutiny. His petition adviser, former state Sen. Ricky Hendon, said campaigns had already obtained Wilson’s petitions for review and argued that his team had checked signatures with the Board of Elections before filing.

Campaign advisers anticipate that candidates may focus challenges on rivals competing for similar voters or on contenders who could draw support from key parts of the city. Victor Reyes, an adviser to Nee’s campaign, said Giannoulias may target candidates with strength along the North Side lakefront, an area considered important in the mayoral contest. Other potential rivalries include Kelly and Mendoza, who are both seeking conservative voters, and Mendoza and Cardenas, the two Latino candidates in the field.

Five candidates who filed within an hour of Monday’s deadline entered a lottery for the final position on the ballot: Pappas, Cardenas, Holberg, Carter-Walters and Ma. Johnson, who skipped the first day of filing, did not enter the lottery for the top ballot position.