Seems to have been a virtual tie between Clinton and Obama: "CNN estimates that, across the Democratic primaries, Barack Obama got 48% of the popular vote and Hillary Clinton 49%."

True enough it's not votes that matter directly but delegates - but if over the next few weeks Obama continues to build support, and ends with significantly more popular votes than Clinton that will put pressure on "super delegates" to go with him.

The point is, the indications are that Obama has succeeded in bringing in people to vote for him who otherwise wouldn't dream of voting for anyone. And if he can do that, it's an awfully big pool of potential votes - non-voters far exceed those who have ever voted for any candidate.