Libertarian Party presidential candidate, former New Mexico Gov. Gary Johnson speaks in Orlando, Fla, in September 2011. President Barack Obama's presidential campaign is paying close attention to two candidates mounting third party campaigns for the presidency, believing they could draw votes from rival Mitt Romney and help the president to victory in a few tightly contested states.

Libertarian presidential candidate Gary Johnson will be on Iowa's ballot in November after officials concluded Wednesday that a state law requiring a convention to get on the ballot is too vague.

A panel made up of Republican Secretary of State Matt Schultz, Democratic Attorney General Tom Miller and Warren Jenkins, the chief deputy for Republican Auditor David Vaudt, voted unanimously to allow Johnson's name to be listed.

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

Johnson's candidacy was challenged last week by two Iowa voters, Gloria Mazza, of Clive, and Dean Montgomery, of Urbandale, who said Libertarians didn't hold a real convention. Instead, the challenge says Libertarians had volunteers persuade fairgoers to sign a document that said they were delegates for Johnson.

Jay Kramer, who said in the documents that he is the Election Day operations director in Iowa for Mitt Romney's campaign, signed the challenge as a witness.

Libertarians say Republicans fear Johnson will pull enough votes from Romney to allow President Barack Obama to carry Iowa. In a very close election, even small states such as Iowa are viewed as important.

The Republican Party and Romney's campaign did not return messages seeking comment.

At Wednesday's meeting, Miller and Jenkins were initially prepared to vote to keep Johnson off the ballot, concluding that Libertarians had not held a convention or caucus. Schultz, however, argued that the law isn't clear in its definitions and that when in doubt open ballot access should prevail.

"We try to give the benefit of the doubt to those people being challenged," he said.

After discussion, Miller and Jenkins were persuaded by Schultz to vote unanimously to allow Johnson on the ballot and send a message to the Legislature to rewrite the law to be clearer.

An attorney for Johnson's campaign, Alicia Dearn, said Schultz put his duty to the office and the people of Iowa above partisan politics.

"The people of the United States and democracy are best served when we have as much open choice as possible. That's what a free election is about," she said.

The attorneys for the challengers did not immediately return calls seeking comment.

Johnson is fighting similar challenges in other states, including Michigan, Pennsylvania, and Oklahoma. He said in an interview Tuesday that he still hopes to be on ballots in all 50 states, which he said requires taking the fight to court when necessary.

"You take it as far as you have to take it," he said.

Richard Winger, a San Francisco-based presidential ballot access expert, said Democrats have a history of challenging minor party candidates and independents as far back as 1936 to keep them off ballots, but Republicans weren't really known to meddle until 2008.

"The Democrats started doing it and now the Republicans have succumbed and it's disappointing," he said. "The American people are just not paying attention. They are losing their right of free choice of whom to vote for."

In previous presidential elections, some third-party candidates have been viewed as spoilers who pulled enough votes away major party candidates to cost them the election.

Some Republicans blame Ross Perot's independent campaign in 1992 for President George H.W. Bush's loss to Democratic challenger Bill Clinton. And many Democrats blame Ralph Nader's Green Party candidacy in 2000 for Al Gore's loss to Republican George W. Bush.