In Background, a Battle for Superdelegates – washingtonpost.com, By Shailagh Murray and Paul Kane

Of the nearly 300 superdelegates who have committed to a candidate, out of a total of 796, Clinton leads Obama roughly by a 2-to-1 ratio, according to numerous counts. The lead is so substantial, her campaign asserts, that even if Obama pulls ahead in pledged delegates after Feb. 5, Clinton will probably retain a modest edge in the overall delegate tally.

But there is a catch. While delegates chosen in a primary or caucus are technically committed to a candidate, superdelegates can change their allegiance at any time. …

While many superdelegates are prominent names in political circles — including Clinton aides Harold Ickes and Minyon Moore — the largest number, a total of 411, are rank-and-file members of the Democratic National Committee — such as local party activists who work in manufacturing and teachers unions — many of whom rose to power during the Clinton administration. These local activists may not bring the same symbolic freight a Kennedy does, but they count equally as superdelegates and are overwhelmingly allied with Clinton.

In the event that Clinton and Obama arrive in Denver for the party’s nominating convention with roughly equal numbers of pledged delegates, superdelegates could make the difference.