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CHICAGO — Monday is the last day for challenges in the Chicago mayoral election on Feb. 26.

Election lawyers were busy Sunday night preparing to file objections to the signatures of some of the 21 candidates’ petitions.

Chicago mayoral candidates need 12,500 valid signatures. All must be registered voters and are only allowed to sign one petition.

Cook County Board President Toni Preckwinkle challenged more than 14,000 names on the petitions for current state comptroller Susana Mendoza. If successful, Mendoza would not have enough to be on the February ballot.

“The reason that she’s being challenged so hard is because she is the leader in this race. When you’re the leader, everybody goes after you.  we are very confident. We will be fine. We have More than enough signatures and we appreciate everyone who signed,” Kathy Byrne, Mendoza campaign co-chair said.

In statement, the Preckwinkle campaign said the following:

“Everyone needs to follow the same rules to get on the ballot.  We understand that this is a daunting process for candidates but it is the first test that every mayoral campaign must pass.”

Also facing a petition challenge is candidate Ja’Mal Green by millionaire businessman Willie Wilson.

“I am appalled that we have Dr. Willie Wilson. A man who claims to be for the people…But a person who says no black candidate should be in the race but him. It’s the most disgusting thing I have ever seen. If you think you can beat me, beat me fair and square on the ballot,” he said.

The last time the mayor’s office was up for grabs, eight years ago, 20 people had filed for mayor. Only six wound up on the ballot after challenges and candidate withdrawals.