Moderator Jim Lehrer sits at his desk before last Wednesday's debate between President Obama and Republican presidential candidate Mitt Romney in Denver. For third-party candidates, getting into a presidential debate is practically impossible. Pool/Getty Images hide caption

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Former New Mexico governor Gary Johnson was nominated as the Libertarian party's candidate for president at their national convention in Las Vegas over the weekend. Joe Burbank/AP hide caption

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Former New Mexico Gov. Gary Johnson announces his plans to seek the Republican nomination for president on April 21. Jim Cole/AP hide caption

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