Barack Obama has netted, to date, 1490 of the 1627 pledged delegates he needs to capture a majority of the delegates elected to secure the Democratic nomination for POTUS. Since the consensus is that the superdelegates will not overturn the majority of the elected delegates, then Obama merely needs to obtain this number of 1627 pledged delegates to achieve victory in the primary process. Obama needs to garner just 137 of the remaining 408 elected delegates, or just 34% of the remaining pledged delegates. This is the magic number, 137, that needs to be focused on in the upcoming weeks, as it is reduced to zero Obama's nomination becomes mathematically assured.
BTW, prior to the PA primary, Obama needed to win 37% of the remaining elected delegates to obtain the majority. So in losing PA, he reduced his required percentage of the remaining elected delegates to the aforementioned 34%. It doesn't seem like much of a victory for Hillary when it's put in these stark mathematical terms. In fact, it demonstrates that PA was a victory for Obama because it brought him closer to winning the nomination, any way you slice it.
There are 187 elected delegates available in NC and IN on May 6, 115 in NC and 72 in IN. Prior to that, there are 4 elected delegates up for grabs in Guam on May 3. WV offers up 28 on 5/13 and then on the 20th of the month 103 are available, with 52 in OR and 51 in KY. Puerto Rico will determine the allocation of its 55 elected delgates on 6/1 and MT and SD will close the primary process on 6/3 with 16 and 15 respectively.
Obama is on the verge of a mathematically deterministic victory. Assuming he acquires 100 of the 191 elected delegates available in the next week's 3 primaries, a conservative estimate, he'll then need just 16% of those remaining to achieve a majority. Odds are that he will reach this tipping point on 5/20, when he is expected to win the OR primary. At this point the super delegates can weigh in and make it official, but even if they decide to wait until the final 3 primaries are complete, the result will at by this time be inevitable.
It's been obvious for some time now that Obama's march to achieving a majority of the elected delegates is unstoppable. This is despite the fact that Edwards still has a handful of pledged delegates under his control. All of the numbers presented above could be reduced to account for this, since in all probability the practical goal is a plurality instead of a majority. However, to avoid any uncertainty and discount the possibility of Edwards endorsing Clinton, a majority of the elected delegates was chosen to determine the magic number of 137.
The total number of pledged delegates available, 3253, does not include those of the MI nor FL delegations, which I feel reasonably certain will not be accounted for until such time as the nomination has been decided.