If the fight goes to the convention, we know the answer: Unless she totally routs Obama in Texas, Ohio and Pennsylvania, her sole remaining path to the nomination depends on convincing the superdelegates to overturn the will of the voters, and convincing the credentials committee to honor the problematic Michigan and Florida elections. So she’ll have to practically destroy the party to save it, or more accurately to save herself. Assuming a possible breaking sex scandal doesn’t bring down McCain, he already beats Clinton by 12 points in the latest poll, while Obama defeats him by 7. If the young voters, independents, and African Americans who Obama’s enlisted in droves stay home in disgust come November, Clinton’s chances would be slim to none.

But she still can do real damage to Obama with her negative attacks in the remaining primaries, particularly in swing states like Ohio. Recent match-ups show Obama a solid victor in states like Pennsylvania, Michigan, Virginia, and Oregon, and dead even in Ohio, while Clinton goes down to defeat in all of them. But depending on how negative she gets and how long the primary battle continues, she could cost the Democrats the election by forcing Obama to spend his time responding to an endless succession of petty attacks, and by giving the Republicans ready-made talking points, like Hillary’s comment that only “one of us is ready to be commander in chief.”

The potential damage is magnified if you count Clinton’s surrogates. At the Youngstown, Ohio rally following Clinton’s Wisconsin defeat, International Association of Machinists President Tom Buffenbarger called Obama supporters “latte-drinking, Prius-driving, Birkenstock-wearing, trust fund babies.” That’s despicable rhetoric, echoing the worst Limbaugh/Fox myths about limousine liberals, while it dismisses the majority of union members who just backed Obama in the Wisconsin and Virginia primaries, or the members of unions like SEIU, The Teamsters, and the United Food and Commercial Workers, who just endorsed him. It also happens to totally steal its language from the sleazy “latte-drinking, sushi-eating, Volvo-driving, New York Times-reading” anti-Howard Dean ads of the right-wing Club For Growth, that helped give us the disastrous candidacy of John Kerry.

If repeated enough, though, those myths have the potential to stick. Clinton supporters have just created a new “527″ political committee, which while technically independent and issue-oriented, is explicitly designed to allow Hillary supporters to evade the standard $2300 donation limits. The group aims to get contributions of $100,000 or more from as many as 100 Hillary donors, so they can pour $10 million in ads into the next round of critical races. Whether or not this is legal, and that’s arguable, no other candidate has done anything remotely similar in this election. And since the ads have no checks of accountability, they’ll be as nasty as their backers decide.

Between Clinton’s actions and those of her surrogates, they might just stigmatize Obama so much that some of her supporters stay home in November, instead of voting for him. They’ll also encourage Republicans and independents who’ve been crossing over to support Obama do the same, or even vote for McCain despite his embrace of Bush’s disastrous policies. I think Obama will still win, so long as his supporters do everything possible to make that happen. But Hillary’s attacks will plant the seeds of doubts. And these will diminish the magnitude of Obama’s likely victory just enough to make far harder for him to pass the major changes we need.

Clinton’s attacks could also make a difference in down-ticket races. Right now, Obama mobilizes huge new constituencies that could elect a wave of new Democratic Senators, Congressional representatives, governors and legislators. But if Clinton manages to damage his appeal sufficiently, he will become far less of an asset even if he still wins. Plus the longer she remains in the race, the more he has to spend money responding to petty attack ads like one in Wisconsin where she accused him of avoiding debates, although he’d already participated in 18 and had two more coming up. It also means, as Tom Edsdall has pointed out, that the Democratic National Committee risks getting so starved of cash because it’s all getting diverted to the nomination fights, that the DNC can’t develop the critical grassroots infrastructure to implement its 50-state strategy.

Hillary may give up if she fares poorly in Ohio and Texas. Bill intimated recently that she had to win both or she was likely done. But she’s talked of fighting all the way to the convention, as have her key strategists, so it’s at least possible that she could keep the race in limbo until less than 10 weeks before the November election, making it far harder for Obama to focus on defeating McCain.

One solution, ironically, could come from the superdelegates. They were established originally as a conservative force in the Democratic Party, a bulwark against grassroots insurgencies like McGovern. In 1984, they actually handed the nomination to Walter Mondale, for his disastrous candidacy, despite Gary Hart’s lead in elected delegates. But they also have an ostensible mandate to consider the Party’s greater good, and if they acted in this fashion, they could play a key constructive role.

Suppose a critical mass of superdelegates did what 400,000 petition-signers asked them to do in a MoveOn/Democracy for America ad that just ran in USA Today — and pledged to honor the will of the voters? Suppose they announced in advance that they’d support whichever candidate had more elected delegates going into the late August convention? Suppose they also came up with a joint solution to the Michigan and Florida mess, where these states lost their delegates by violating a Democratic Party agreement on when states could hold their primaries? It would be a travesty to validate their sham elections given that the candidates couldn’t even campaign in Florida, that Obama and Edwards had pulled their names from Michigan ballot, and that Clinton herself told New Hampshire Public Radio that her staying on the Michigan ballot was irrelevant because Michigan’s vote “is not going to count for anything.”

But what if the superdelegates acted now, to make clear that they will not validate those two elections as they stand, and that they’ll encourage their colleagues on the Credentials Committee to do the same? As an alternative, they could urge those two states to do what the DNC has already suggested, and rerun their elections as caucuses. Yes, this would cost some money and effort, but if the experience of the states that have held them is any guide, it would also offer a major chance for the party to mobilize and engage new supporters, and it would bring participants together in a way that reminded them of the values they shared in common. If the two state parties, both dominated by Clinton supporters, still refused to go along, the superdelegates could also offer the alternative of simply seating Clinton-Obama delegates 50-50, to make it a dead wash. But they need to make clear that Clinton won’t be able to pull out a last-minute victory by gaming the rules.

Facing a relatively united bloc of precisely those superdelegates that Clinton still hopes to win, I suspect she’d be far more likely to quit, and do far less damage while still in the race. Key party elders like Al Gore and Nancy Pelosi are already working to ensure a convention process that pulls the Party together, rather than splitting it apart. They and others might play an additional role by speaking out against destructive negative campaigning (whether by Clinton or her surrogates), and making clear that if this goes too far, she will lose their support.

Were Hillary running less of a scorched-earth campaign, it could continue onto the convention without major damage. But she’s pursued this approach from the moment Obama emerged as a serious challenger, and seems only to be reaffirming it more in recent weeks. That means that if Democrats really want to avoid a divisive fight, they’d do well to unite around Obama now. He just got the endorsement of the 6-million member Change to Win Coalition (and individual member unions like SEIU, the United Food and Commercial Workers, UNITE/HERE, and the Teamsters). The United Steel Workers, a national social justice leader, initially endorsed John Edwards, and will make a decision at their next board meeting. It’s time for the other major industrial unions and progressive organizations to commit too, or to reconsider their earlier support for Clinton.

That’s also true of prominent individuals, like Edwards. In fact, I originally supported him, and gave him more money than I ever had to any previous candidate. But it’s now well overdue for him to encourage his supporters to back the legitimate inheritor of his quest for change. Maybe Clinton will still make an improbable comeback, but the longer she keeps campaigning, the more attacks and divisiveness we’ll see. The more party leaders speak out to prevent this from happening, the less risk that she’ll create lasting damage in her desperation to hold onto a prize that’s now almost certainly slipped away.

Paul Rogat Loeb is the author of The Impossible Will Take a Little While: A Citizen’s Guide to Hope in a Time of Fear, named the #3 political book of 2004 by the History Channel and the American Book Association. His previous books include Soul of a Citizen: Living With Conviction in a Cynical Time. See www.paulloeb.org To receive his articles directly email sympa@lists.onenw.org with the subject line: subscribe paulloeb-articles