DES MOINES, Iowa (AP) -

Libertarian presidential candidate Gary Johnson's effort to be listed on the Iowa ballot in November has been challenged.

Documents challenging Johnson's candidacy were filed Friday by three individuals including Jay Kramer, who says he's the Iowa election day operations director for Republican Mitt Romney's campaign.

Republican Secretary of State Matt Schultz scheduled a hearing for Monday afternoon. Shultz, a representative from the state auditor's office, and Democratic Attorney General Tom Miller will decide whether to uphold or deny the challenge.

Libertarians say they held a state convention at the Iowa State Fair to get Johnson, the former Republican governor from New Mexico, onto Iowa's ballot.

The challenge says Libertarians didn't hold a real convention or sign up actual delegates.

Candidates must be certified for Iowa's ballot by 5 p.m. Wednesday.

(Copyright 2012 by The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)

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