You may recall that in the wake of Super Tuesday, the Obama campaign accidentally sent a reporter for Bloomberg a spreadsheet that included the campaign's predictions on how the vote would turn out in each of the remaining primaries and caucuses. The memo was unique in its ability to give us a window into the Obama campaign's expectations about how they viewed the upcoming contests playing out. This was not the campaign's spin designed to set expectations for the news media; these were their actual expectations.
Now that we've had several contests since the memo was released, it is even more clear how costly the month of February was for the Clinton campaign, which struggled to compete at a level that even the Obama people expected. The figure below plots the share of the vote that the Obama expected to get in each state (based on their memo released just after Super Tuesday) against the share of the vote Obama actually received. States falling along the line would be those in which Obama did just as his campaign expected him to do. States falling above the line are those in which Obama's actual voted total exceeded his campaign's expectations, and those below are where he failed to meet those expectations.
The striking point one can take from this figure is that much of Obama's lead was generated by his ability to not just win a lot of states in February, but to win them by larger margins than his campaign expected him to. In Virginia, DC, Washington, Nebraska, and Maryland, Obama performed significantly better than his campaign had expected. His campaign expected to lose Maine narrowly, but he won the state easily.
What happened? Why was Obama able to perform so much better than his own campaign thought he would? One reason for this is the fact that the Clinton campaign appeared to approach the Democratic primaries as if they were winner-take-all. Essentially, she chose not to campaign heavily in states where she didn't think she could win. Yet, in a race where delegates are allocated proportionally, failing to compete may have cost her more delegates in a number of states that she was going to lose. For example, she all but ignored the Potomac Primary states (VA, MD, and DC), and Obama took advantage by not just winning those states, but winning them by large margins that netted him significantly more delegates than his campaign expected. In fact, this happened throughout the month of February until Clinton's "Alamo moment" on March 4th.
Clinton competed heavily in the March 4th primaries, understanding that this was her last opportunity to stay in the race. And what happened as a result? Well, the actual vote totals received by Obama fell back into line with what his campaign had originally expected. In fact, the predictions generated by Obama's strategists a month earlier were exactly correct for Texas, and just barely off for Ohio, Vermont, and Rhode Island. The bottom line: when Clinton competed in a state, the predictions largely matched the actual outcome. Where Clinton got into trouble was failing to compete in several states between Super Tuesday and March 4th, a period during which the Obama campaign exceeded their own internal expectations and built the delegate lead that Clinton is now trying desperately to overcome.