To the already too long list of Hillary Clinton’s enemies and foes, it is time to add another entry: math. Simply put, it is almost mathematically impossible that, between now and the final Democratic presidential contest—the Puerto Rico caucus on June 7—she will be able to overcome Barack Obama’s lead in pledged delegates. Even the most pro-Hillary scenarios of how the next three months play out—with her sweeping the remaining 12 contests, including a 20-point blowout win in delegate-rich Pennsylvania—still result in her trailing Obama by more than 50 pledged delegates. (Throw in large wins for her in hypothetical revotes in Michigan and Florida, and Obama’s lead gets smaller, but it’s still there.) And realistic scenarios—does anyone really think Obama will lose Mississippi and North Carolina?—show Obama’s delegate lead to be even more insurmountable. As Clinton’s chief strategist cum outside message adviser Mark Penn put it bluntly in a memo last month, before math had revealed itself to be Hillary’s bitter rival: “This election will come down to delegates.”

But, like so many of Hillary’s foes, the mathematical case against her candidacy has a glaring—and perhaps fatal—weakness: According to the rules of how the Democratic Party picks its presidential nominee, pledged delegates aren’t all that count. In addition to the 3,253 delegates awarded through primaries and caucuses, there are 795 superdelegates up for grabs. And, while some, including the Obama campaign, argue that these superdelegates should honor the will of the voters—and thus back the candidate who won the most delegates in the primaries and caucuses—there is nothing in the rules stipulating that they must. Indeed, on the contrary, superdelegates were created, in part, to serve as the Democratic establishment’s check on the will of the voters; they can back whomever they choose.

Which is why calls for Hillary to withdraw—calls that invariably rest on the mathematical case against her candidacy—are premature. By winning Ohio and Texas, Hillary won the right to continue in this race. And, as she and Obama campaign in the days and weeks ahead, their battle over pledged delegates will almost be something of a sideshow, since at this point neither one will be able to win enough pledged delegates to give them the 2,025 delegates needed to secure the nomination. Instead, both Clinton and Obama will be using the contests in North Carolina and Oregon, Pennsylvania and Puerto Rico as vehicles to make their case to superdelegates, who, because of the tightness of this contest, will ultimately decide its winner.

Of course, the odds of Hillary winning enough superdelegates to her side to win the nomination are long. Although there’s no rule saying they must obey the will of the voters, many superdelegates likely will do just that—meaning that, if Obama can maintain his lead in pledged delegates, he’ll likely hold an edge in superdelegates. Hillary’s only hope is that her performance in the coming weeks is convincing enough—and Obama’s unconvincing enough—that she can create a sense of momentum that, in turn, causes a groundswell of superdelegates to move in her direction.

But, again, that is a long shot—which is why it’s imperative that, as Hillary Clinton continues her campaign, she conduct it in a certain manner: She can’t run the type of campaign she ran in the lead-up to Ohio and Texas. For weeks, Clinton attacked Obama with a relish not previously seen in this race. But it wasn’t the fact she was attacking Obama that was problematic, it was how she was attacking him—namely, in a way that will make it more difficult for Obama should he, as is still likely, be the Democratic nominee in November. For instance, it would have been fine for Hillary to argue that she’d make a better commander-in-chief than Obama; but it was wrong for her to essentially argue, as she did on more than one occasion, that she and John McCain would make better commanders-in-chief than Obama. Similarly, her strange hedging on”60 Minutes" about whether she believes Obama isn’t a Muslim only added fuel to the unfounded rumors that are already circulating about his faith. Frankly, Clinton’s chances are slim enough that a win-at-all-costs mentality from her campaign is not worth the risk of doing irreparable damage to the candidate who will likely be her party’s nominee.

But how to ensure that Clinton runs the right sort of campaign from here on out? As the results in Ohio and Texas proved, the voters won’t punish her for these sorts of attacks on Obama; in fact, they seem willing to reward her for them. But there is one group who can enforce this new set of rules, the people Hillary will need if she has any chance of realizing her slim hopes of winning the nomination: the superdelegates. Superdelegates are free to support whichever candidate they choose; the only requirement they labor under is to act in a way that they believe is for the good of the Democratic Party. And it’s clearly in the party’s best interest that the rest of its nomination fight be conducted in a manner that doesn’t benefit the Republicans. That’s why superdelegates must watch the Clinton campaign closely in the coming weeks, and, should she continue to attack Obama in a fashion that’s no different from the way McCain would, these superdelegates should begin committing to Obama. At this late date, the odds are so slim that Clinton can win that it’s far too risky for her to try to achieve victory by tearing Obama down. Fortunately, the very people who are Hillary’s last best hope can make certain that she doesn’t go that route.

This article appeared in the March 26, 2012.