Ald. Marty Quinn (13th) on Saturday withdrew his bid to strong-arm a 19-year-old challenger off the ballot with a petition objection that drew accusations of Chicago machine-style political fraud.

DePaul University student David Krupa was required to collect 473 signatures to appear on the ballot against the incumbent Quinn, a top ally of powerful Illinois House Speaker Michael Madigan who has held the Southwest Side seat since 2011.

But before Krupa had even filed his petitions, Quinn supporters filed nearly 3,000 affidavits allegedly signed by people seeking to revoke their signatures for Krupa — despite the fact that the teen collected only about 1,700 signatures, Krupa’s election attorney Michael Dorf said.

Only 187 of the signature revocation affidavits actually matched signatures on Krupa’s petitions sheets, Dorf said, meaning a little more than 2,600 were potentially fraudulent.

It wasn’t until Dorf filed a Freedom of Information Act request with the Chicago Board of Elections that he learned of the thousands of extra affidavits. He said he’d never seen anything like this before.

Dorf said Michael Kasper, Quinn’s attorney, called him Saturday morning to tell him they’d withdraw their objection. Kasper could not immediately be reached for comment.

A spokesman for the Chicago Board of Election Commissioners confirmed Krupa’s spot on the Feb. 26 ballot was secure.

Dorf said Krupa was “delighted” about the news.

“All David ever wanted was a chance to face [Quinn] one-on-one and test their ideas against each other,” Dorf said. “He’s pleased. Now he’s ready to run a campaign.”

CHICAGO ELECTION COVERAGE:

• Joyce, Daley mayoral match-up goes another round, threatens families’ ties

• Preckwinkle’s petition pounce: Challenges Mendoza, four other women

• Signature accomplishments: A mix of strategy and superstition in petition filing

• A game of 21: Mendoza, Brown join crowded mayoral field — now who will fold?