CHICAGO (CBS) — David Krupa, a candidate for 13th Ward Alderman in Chicago, says he has faced intimidation, harassment and threats while challenging the alderman allied with House Speaker Mike Madigan, and now he’s filed a federal lawsuit to hold Madigan accountable.

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Krupa says after he started passing petitions to get on the ballot, his precinct captain delivered a dark message.

“‘You know Dave, you’re a good kid, and you got a bright future, but I’d hate to see something bad happen to you,’” Krupa said.

That’s one of the reasons behind Krupa’s federal lawsuit against Madigan and Alderman Marty Quinn. Another reason is alleged deception.

“People feel violated by this,” Krupa said. “People feel like they were lied to, like they were strong-armed.”

Some 13th ward voters were encouraged by Madigan’s foot soldiers to sign petitions to remove Krupa from the ballot while being misled about what they signed.

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Voter Brian Palsone didn’t seem to realize his signature on the petition was to remove Krupa from the ballot.

“Well, I guess I made a mistake signing it then,” he said.

And the lawsuit contends Madigan’s forces committed outright fraud by presenting thousands of signatures to kick Krupa off the ballot, from voters who never signed to put him on in the first place.

“You don’t have to be a mathematician to know the numbers don’t add up,” Krupa said.

Quinn wouldn’t appear on camera but said, “This lawsuit is just an effort to distract voters from my opponent’s extreme right wing agenda. ”

“Distracting voters with ludicrous claims is pulled directly from the ultra-right wing playbook. The residents of the 13th ward deserve better,” Madigan said.

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Krupa calls himself a moderate independent with no party affiliation. However, he’s hired attorney Tony Peraica, a former Cook County commissioner and a Republican, to fight his lawsuit.