Barack Obama has excommunicated himself. See here for the New York Times story. Key paragraph:

“Our relations with Trinity have been strained by the divisive statements of Reverend Wright, which sharply conflict with our own views,” they [the Obamas] wrote. “These controversies have served as an unfortunate distraction for other Trinity members who seek to worship in peace, and have placed you in an untenable position.”

Translation: Wright is starting to hurt my electoral prospects.