Back in May, when Americans Elect, the group formed to put a bipartisan third party ticket on the 2012 presidential ballot, closed shop, everyone stopped talking about whether a third party candidate would enter the race in 2012 -- and the focus since then has been on Obama and Romney in a two person race.



This two person race has been a dead heat for months, and most people expect this to be one of the closest presidential races ever. (The latest Real Clear Politics poll average has Obama at 45.9% compared to Romney at 44.8%.)



But here’s the thing -- the 2012 election isn’t really a two person race. There’s a third party candidate out there -- and he could derail either one of the two major party candidates' shot at the White House.



His name is Gary Johnson, the former governor of New Mexico and the Libertarian Party candidate.



If that seems doubtful, remember that Ralph Nader didn’t crack 3% of the popular vote in 2000 -- yet he completely changed the outcome of that race.



Gary Johnson, meanwhile, is currently polling at 5.3% in the latest Zogby national poll.



ASKING THE WRONG QUESTION



When people think of third party candidates and the presidential race, they often ask the wrong question: Can they win?



The answer, so far, has been no. Ross Perot’s on-again, off-again candidacy in 1992 largely self-destructed (though he did still win 19% of the popular vote), and Ralph Nader received just 2.74% of the popular vote in 2000.



But the relevant question isn’t whether a third party candidate can win -- it’s whether they can effect the final outcome of the race.



In 1992, Perot’s drew much of his 19% support from George H.W. Bush -- and sent Bill Clinton to the Oval Office with just 43% of the popular vote.



Ralph Nader’s 2.74% in 2000 didn’t stop Al Gore from winning the popular vote nationally. But his 97,000 votes in Florida were more than enough to derail Gore in the controversial Florida recount -- ultimately throwing the Electoral College and the presidency to George W. Bush.



Could Johnson play a similar role in 2012?



AN OUTSIZED INFLUENCE IN SWING STATES



It’s true that Johnson barely made a dent when he ran in the Republican primary in 2011. He only appeared in a single televised debate, never broke 2% in any of the major polls, and dropped out before the first votes were cast in New Hampshire.



But Johnson could make a major dent in the general election -- because he is currently doing better than most people realize in several key swing states.



Most pollsters don’t even include Gary Johnson in their polling. But recent polling that included him showed Johnson drawing 9% of the vote in Arizona, 7% in Colorado and New Hampshire -- and 13% in his home state of New Mexico.



All of these are key swing states. And such numbers give Johnson the chance to be a giant killer in the 2012 race.



But the question is, which giant?



DOES JOHNSON HURT ROMNEY, OR OBAMA?



At first glance, it would appear that Johnson’s candidacy hurts Romney the most. Take Arizona, for example -- a state that Romney needs to keep safely in his column if he is going to win the White House.



In Arizona, Romney goes from a 50-43 advantage over Obama to just a 45-41 advantage when Johnson is included -- within the margin of error, in a state that Romney should have locked up.



And in many other states, Johnson’s Libertarian support comes largely from Republican-minded voters, as one might expect.



But Gary Johnson could also present a threat to Obama’s re-election chances.



In Colorado -- which the Obama campaign has been working hard to hold onto in 2012 -- Obama currently leads Romney 49-42 in the latest PPP poll, down from a 53-40 in April.



But add Gary Johnson to the mix, and Johnson’s 7% support in Colorado pulls almost equally from both candidates, dragging Obama down to 47 percent and Romney to 39.



If that still seems like a safe margin for Obama, remember that Obama’s Colorado strategy relies on the enthusiastic turnout of college educated white voters, minorities, and youth. Then note that Colorado has a marijuana legalization initiative on the ballot in November -- a fact that could further bolster youth turnout for Johnson, who supports marijuana legalization.



And in his home state of New Mexico -- another Western state that the Obama camp wants to hold in 2012 -- Johnson actually pulls more from Obama than from Romney, changing a 49-44 advantage for Obama in the latest poll to a too-close-to-call 42-38 advantage for Obama, with Johnson taking 13%.



ASKING THE RIGHT QUESTION



Polling thirteen percent in your home state, of course, doesn’t bode well for your chances at winning the White House. But remember, the question isn’t whether Johnson can win the White House -- he won’t -- but whether he can change the outcome of the race.



It’s clear that he can. In just the few key swing states where he’s been included in polling questions, he’s far outperforming the typical Libertarian candidate of years past. (Libertarian candidate Bob Barr, for example, barely got one half of one percent of the vote in states like Arizona and Colorado in 2008.)



We have no idea of what happens when you add Gary Johnson to presidential polls in places like Ohio or Florida or Iowa.



Nobody knows, because few pollsters have bothered to ask the question. (In swing-state Wisconsin, Johnson was drawing 5% in May -- largely from independent voters.)



What’s clear about Gary Johnson at this point is that if the race remains this tight, he's going to be a problem for somebody, somewhere.



We don't yet know which candidate he might harm the most -- but both campaigns should be looking over their shoulders at that guy almost nobody is talking about.



Let me know what you think on Twitter @joetrippi.