The presidential election could well turn on a factor that has gotten virtually no discussion this year - the votes drawn by Libertarian Bob Barr, Green Cynthia McKinney and independent Ralph Nader.
The most recent polls show a race too tight to call: Gallup tracking from Sept. 23 showed Sen. Barack Obama with 47 percent to Sen. John McCain's 44 percent. More interesting is a CNN/Opinion Research poll released Sept. 22 that included all five candidates for president. Mr. Obama was at 48 percent, Mr. McCain was at 45 percent, and Mr. Barr, Ms. McKinney and Mr. Nader were polling a combined 6 percent of the vote. (Mr. Nader captured 4 percent and Mr. Barr and Ms. McKinney each got 1 percent.) In a close contest, the support for any of these three could well decide which major party comes out ahead nationally and in key swing states.
Indeed, the most recent state polling from CNN/Opinion Research to include third-party candidates bears this point out. Taken earlier in September, the poll found that in Missouri, where Mr. McCain had a four-point lead, Mr. Nader had 3 percent and Mr. Barr had 2 percent. In New Hampshire, where Mr. Obama had a five-point lead, 48 percent to Mr. McCain's 43 percent, Mr. Nader had 4 percent and Mr. Barr had 2 percent. In Michigan, where Mr. Obama led Mr. McCain by only two points, Mr. Nader has 6 percent and Mr. Barr 2 percent.
Other polls suggest an even more dramatic situation brewing, with Mr. Barr as Mr. McCain's biggest third-party concern. Zogby International polls this summer showed Mr. Barr approaching 11 percent in New Hampshire, 10 percent in Nevada and 8 percent in Ohio.
What accounts for such levels of support?
Most important, there is widespread - and growing - dissatisfaction with the major parties in America. Mr. Obama has had to go negative, Mr. McCain has flip-flopped time and again from the maverick of old to the GOP's status quo, and the "Palin effect" is wearing off as Alaska Gov. Sarah Palin's politics appear to be no different from those inside the Beltway. As the major-party candidates show their true colors, many voters will start turning toward third-party alternatives.
There's also a wild card: Rep. Ron Paul of Texas, who sought the GOP nomination and has continued to attract fervent supporters to his "Campaign for Liberty" attacking big government and the two-party system. Last week, Mr. Paul threw his support behind yet another alternative party candidate, Chuck Baldwin of the Constitution Party. With Mr. Barr having raised nearly $1 million and becoming a growing presence in many states, adding a Paul-supported Mr. Baldwin to the mix could be disastrous for Mr. McCain, who could lose votes to both alternative candidates.
History has shown that third-party candidates can gain a large percentage, as in the case of Ross Perot, who reached close to 20 percent of the vote in 1992, and George Wallace, who almost gained 14 percent of the vote in 1968. But neither of those had the impact of Mr. Nader's single-digit percentage in the 2000 election. Mr. Nader's 90,000 votes in Florida were a crucial factor in an election that came down to George W. Bush's victory in Florida by slightly more than 500 votes.
As the polls stand now, with Mr. Obama holding slight leads nationally and in many swing states, Mr. Nader's 4 percent could siphon off enough votes to thrust Mr. McCain into the White House. That said, if Mr. Barr steals 8 percent of the Ohio vote from Mr. McCain, Mr. Obama will almost certainly win the presidency.
So in the waning days of the election, it's not the biggest poll percentages that demand scrutiny, but the smallest ones. Because it could turn out that the crucial role in the 2008 election will be played by a candidate no one is talking about.
Douglas E. Schoen, a pollster and former adviser to President Bill Clinton, is the author of "Declaring Independence: The Beginning of the End of the Two-Party System." This article originally appeared in the Los Angeles Times.