It's interesting to see how this one plays out. Of course, a huge gap between an exit poll and a final vote tally is normally a sign of a stolen election but the Democrats can't seem to get their heads around the notion that their own side might be guilty of election fraud instead of the Repugnicans. Admittedly, with a clear record of Republican election skullduggery in the Bush years, it's hard to see how two different factions could each seize control of the voting apparatus within such a short space of time.
But Hillary stealing the election from Obama isn't the only possible interpretation of events. It's possible that the Republicans stole the election on Hillary's behalf. Why? Well, obviously they must have done some private polling which told them Hillary would be easier to beat than Obama in the presidential election. The public polls I've seen would bear this out. Hillary has a lot of entrenched antagonism built up already thanks to her husband's spell in the oval office. Obama is much more appealing to independents and other undecideds.
The Dems forget that the Repugs have a long track record of trying to select their own opponents. They should refresh their memory of some of the dirty tricks Nixon's people got up to to try and derail the campaign of Edward Muskie, who, private polling showed, could beat Nixon in the election, and promote the candidacy of George McGovern, who, however worthy, was deemed easy to beat because he was out of touch with the mood of the country.
In the end, after a strange incident in which Muskie was perceived to have become overly emotional (shades of Hillary but with the opposite apparent effect), his campaign withered and died. McGovern won the Democratic nomination and was trounced in the election. There are those who believe that Nixon's black bag men slipped a mickey to Muskie, putting LSD in his drink or something similar, to push him over the edge. You can read more about that in Lisa Pease's article here. Skip to the section titled "Dirty Tricks in '72".