Progressive voters leaning towards Ralph Nader or other third-party candidates could make the difference between Barack Obama winning or losing the presidency.

Being marginal myself, I am very aware of how decisive third-party voters can be. I won the Democratic nomination to the California Senate by less than one-percent in 1992. In the final two weeks, I mailed out an appeal to Green Party voters in my district, urging them to switch parties in order to vote for me. The mailer included cards to re-register from Green to Democrat for the primary, and another card to register again as a Green once the primary was over. Those hundreds of votes made the difference.

Late in 2000, I found myself enmeshed in torrid conversations between the Gore and Nader campaigns. The process wasn’t good. The Democrats were trying to push Nader off the ballot anywhere they could, thus refusing to recognize his core interest in establishing a new party. The Nader people refused to acknowledge that there was any difference between Gore and Bush, and denied that their votes could affect the outcome. My “Gore-Nader” proposal–that Nader endorse Gore in Florida and other close states, and become our most important progressive advocate in Washington after a Gore victory–went nowhere, because Nader would have none of it.

So much was at stake in 2000 that, to this day, the wounds then inflicted have not healed. One side (in the tens of millions) believes that Iraq and the Alito Court would have been avoided and the first environmental presidency would have been launched. The other side (a few thousand) denies that the Nader vote caused Gore to lose Florida.

Rather than scrape those scabs one more time, my proposal is that progressives thinking of voting third party this time consider the historic chance to elect Barack Obama president. Such an open gesture would be enormously important to the people who most fervently favor Obama–young people, African-Americans, Latinos, and labor, for example–and go a long way to heal and unify the progressive movement this time around.

Many of those Obama supporters share the criticisms of Obama made by the third-party advocates–that he needs to apply more pressure on Iraq, Afghanistan, Pakistan, domestic spying, trade. But there is no sympathy, no comprehension–only something between irritation and rage, towards the third-party view that it doesn’t matter if John McCain wins and Barack Obama loses.

It is hard for many people to grasp that an infinitesimal fraction of voters could deny progressive hope and revive the failing fortunes of the neoconservatives and the right-wing evangelicals. It is also possible that Obama, fueled by the Wall Street economic scandal, will pull away, in which case everyone can vote their first preference.

But with twenty-nine days left before the election, it is crystal clear that racism and other forms of submerged resistance are blocking an Obama runaway victory.

If this race is like 2004, here are some reminders of how close it will be. Democrats lost Iowa by 10,059 votes, or .67 percent. Democrats won Wisconsin by 11,384 votes, or .38 percent, and New Hampshire with 9, 274 votes, just 1.37 percent.

Now look at today’s electoral map, as detailed by RealClearPolitics.com . Obama leads by 6 percent, 49.3-43.3 in a national average, by 4 percent in the ABC-Washington Post calculations, and only 3 percent in the Democracy Corps poll. When you include and Nader and Bob Barr in the count, Obama’s 6 point lead is cut by nearly one-third, to 4.2 percent (47.5 percent over McCain’s 43.3 percent, with Nader at 2.5 percent and Barr at 1.5 percent.) Cynthia McKinney and others are not included.

These projections cannot estimate the numbers of new voters or the turnout of African-Americans who will offset Obama’s losses among some conservative Democrats. But neither can they fathom whether 6 percent of white voters who say they are voting for Obama will wind up secretly voting for the white man, which is the historic pattern.

That means that the national numbers, for now, are dead even. If that pattern holds, the third-party left can make a big difference in ensuring a majority vote for Obama by increasing their support in safe states like California and New York.

When we get down into the key electoral college states, it doesn’t matter if solid red-state voters drift from McCain to Nader or others. Where it matters decisively is in states like Florida, Ohio, Colorado, Nevada, New Mexico and North Carolina, where there are crucial progressive pockets.

At this point, the map shows these states too close to call: Ohio, Obama by 3 percent Wisconsin, Obama by 5 percent Virginia, Obama by 4.9 percent Florida, Obama by 3 percent Colorado, Obama by 3 percent Nevada, Obama by 1.8 percent Indiana, McCain by 2.2 percent North Carolina, Obama by 0.5 percent

Perhaps these states will turn decisively to Obama. We may know in ten days. But at this moment, the Obama movement needs all the votes at the margin.

Third-party voters should watch the polls very carefully, and think long and hard about the choice presenting itself.

In the face of McCain-Palin, is it possible to argue that there is no difference between the candidates this time? Is it really credible to argue that voting for Nader individually doesn’t matter because it doesn’t matter to the outcome, which seems to be Nader’s argument for the 2000 Florida result?

In addition to voting for Obama, third-party activists can make a huge local difference in fighting to see that every vote counts in states with unreliable registrars, histories of stolen elections and long, cold lines on election nights. This will be a street battle for democracy that citizens of every persuasion should engage in.

In the end, the only question in November is the basic question of which side you are on, a question that goes back decades and centuries and which this generation has the historic opportunity to answer.