Bob's post below, jumping off from Digby, makes the important point.
And here's the thing: Clinton is, by any historical measure, not a uniter. She and her husband both have a long track record of sowing division and reaping the (short terms) rewards. Obama has been making this point on the campaign trail:
“Keep in mind, we had Bill Clinton as president when, in ’94, we lost the House, we lost the Senate, we lost governorships, we lost state houses,” he said. “And so, regardless of what policies they wanted to promote, they didn’t have a working majority to bring change about.”
More to the point, Clinton's modus operandi as a politician is to prepare for the negative, for the attack. This excellent diary at kos by davefromqueens lays out how the Clinton campaign has done a thorough, Rovian vetting job on Obama.
I urge you to read the whole diary, but here's the wrap-up:
Obama attracts that support because people of both parties and of all different political persuasions are sick and tired of the establishment, the corporate media, and Washington cocktail party insiders telling the American people what they can and can not do. They are sick and tired of these establishment politicians putting themselves ahead of the real interests of the American people.
Obama symbolizes the return of people oriented politics, a person who wants to be President to help others, even if he is not as progressive as I would like him to be. He offers change after 28 years of either a Bush or Clinton in the White House. Yet the establishment and the insiders have attacked him relentlessly, led by the Clinton campaign.
Obama is battled tested. Obama is equipped to handle Republican type smears. He's already done it.
Bottom line: Obama is the unifier. And the voters are telling us that with their votes.