Never mind reality. What if she racks up a string of late-season primary wins?

Two arguments are at the center of the Clinton campaign's last-ditch attempt to seduce the 800 unpledged delegates who will determine the nominee at the Democratic convention. The first plays to the raison d'être of the superdelegates, created in 1982 to steer the nomination away from a leading candidate in case he or she fumbles late in the nomination race, hurting the party's chances of beating the Republican nominee in November.

"[Hillary] has the best chance to defeat John McCain," Bill Clinton says. Why? Because she's vetted. All the dirt has been dug up on her; the GOP won't dredge up anything new. As for Obama, his friendships with Reverend Wright and a Chicago slumlord might represent the mere tip of a toxic Daley Machine sludge pile.

Clinton's second argument is her novel promise to win the "primary popular vote," a phrase no one heard of before. Obama leads by 700,000 out of 26 million votes cast; Hillary says she'll close this gap in Pennsylvania.

The Democratic Party probably won't risk alienating its most reliable constituency. Probably.

But what if it does? Left-of-center insiders, mainstream Democrats and street activists alike, are quietly worrying that things could turn ugly. 1968 ugly. Maybe even worse.

"If party insiders fix the nomination against the will of the people--when the entire election is about repudiation of the old politics--it will be an act of monumental political disaster that historians will condemn for generations," Brent Budowsky writes at TheHill.com. Hillary Clinton would have a tough time uniting the Democratic vote against McCain, still coasting on the fumes of his pre-Bush rep as a straight-shooting maverick.

There would certainly be street protests in Denver. "I will, without doubt, march at the convention if there is even a remote chance on the nomination being stolen," promises a typical poster at the liberal blog Daily Kos.

Blogger Al Giordano predicts: "It won't be the chaotic street protest and battle with the cops that occurred in '68: we've learned too much from that. It will be organized, Gandhian in its adherence to discipline and nonviolence, and more massive than anything maybe ever seen in the United States' long history of social movements. If the party leaders choose to destroy democracy by denying the fair-and-square winner the nomination, democracy will then be duty bound to destroy the party...The big news is that, for the first time in decades, a black-white alliance from the street will be possible: Montgomery 1955 meets Seattle 1999 in Denver 2008."

Street protests + rage = ?

No one knows whether angry Obama supporters would turn violent if their man is denied the Democratic nomination. But precedents count. The last time American progressives got worked up about anything was the invasion of Iraq. They marched by the millions. They kept things "Gandhian." But non-violence failed: The media ignored them. And the war dragged on--longer, so far, than World War II.

More recently, on the international front, activists can't ignore events in Tibet, where the passage of time has merely accelerated the oppression of the indigenous population at the hands of Chinese occupation troops. Ultimately, young Tibetans are finding violent resistance to be more effective--and more attractive to television cameras--than the Dalai Lama's corporate-approved militant pacifism. If they keep Chinese cities burning through the summer Olympics, Tibetans could win their independence this year.