John B. Anderson in 1980 and H. Ross Perot in 1992 both ran as independent centrists, and while they weren't the only reason the incumbents lost (Ronald Reagan won a majority of the popular vote in 1980), they were certainly a factor.
President Obama might fare in a two-candidate race. Could Obama beat Mitt Romney? Rick Perry? Herman Cain? (In all three cases, the answer is probably yes.)
But there's likely to also be a wild card in this election. Americans Elect, a well-funded "virtual third party," plans to put a centrist presidential candidate on the ballot in all 50 states, and while he or she is unlikely to win the presidential election, the presence of a third candidate could still have a major impact on the outcome.
Americans Elect is a collection of Republicans, Democrats and independents who say they're fed up with the polarization that has poisoned American politics. Some of its backers have previously contributed to Obama, Romney or other candidates. Several are fans of New York Mayor Michael Bloomberg, who has flirted with the idea of running as a third-party centrist. The group's central figure is Peter Ackerman, a wealthy investor and former banker who considers himself an independent and who was active four years ago in a similar effort called Unity08.
The group plans to hold a national primary election on the Internet — a mass-participation exercise that anyone can join. Candidates can nominate themselves, and voters can form committees to "draft" candidates, including politicians drawn from the major parties — Hillary Rodham Clinton, for example, or Jon Huntsman. Candidates who don't want to be drafted can take their names off the ballot, but only after several rounds of voting — so a Clinton boomlet could happen even if the secretary of State says she's not playing. Meanwhile, the group is collecting signatures to put itself on every state's ballot; it says it has collected 1.6 million signatures in California, which should enable it to qualify.
Who will its candidate be? Bloomberg is frequently mentioned, even though he says he doesn't plan to run. So is Huntsman, even though he says he's only interested in the Republican nomination. It might be former Louisiana Gov. Buddy Roemer, who has been trying to break into the Republican race; former Sen. Evan Bayh (D-Ind.), who retired after denouncing both parties; or independent business figures such as Starbucks CEO Howard Schultz, who has called on his fellow moguls to stop giving money to politicians.
Americans Elect says it plans to choose a presidential nominee (and a vice presidential candidate, who by the group's rules can't come from the same party) by June.
What happens then depends mostly on the shape of the contest between the Democratic and Republican candidates.
A candidate like Bayh might draw disaffected moderate and independent voters away from President Obama, making it easier for a Republican like Romney to win. Or a candidate like Bloomberg could attract moderate Republicans if the GOP nominee is seen as too extreme a conservative, a scenario that would benefit Obama.
Both Democrats and Republicans in Americans Elect insist that there's no conspiracy here. They don't have a preferred candidate, they say, and they're not launching this effort with a "spoiler" outcome in mind.
"I'm in this because I think the system is broken, and this is a way to begin fixing it," said Darry Sragow, a Los Angeles lawyer and veteran of California Democratic politics who is the group's national political director. "There's no intention here to spoil anybody's candidacy."
On the other hand, he acknowledged, that could be the effect. "The law of unintended consequences is alive and well," he said.
One potential pitfall for this well-intended effort is the opportunity for mischief. Americans Elect, because of recent court rulings, doesn't have to report who its donors are. Its organizers don't intend it to become a spoiler, but Republicans or Democrats could flood it with money to try to make it one.
Another is that the group is aiming at the wrong target. Presidential elections aren't the main source of polarization in American politics; neither Obama nor Romney is an extremist. Most of the polarization we're seeing comes from Congress, where districts have been drawn to protect incumbents and where donors and interest groups have more influence on the nominating process.
The group's organizers say they understand that. "To change the system, you have to change it at the level of Congress and state legislatures," Sragow said. "But we think the national level is the best place to get started."
That start is certain to be an interesting experiment no matter what happens. But its real potential will come in 2014 and beyond — if it can stay on the ballot and break the two parties' oligopoly in congressional elections, where the real problem lies.