“The intersection of Duke Energy’s interests and its support for the convention is testing Mr. Obama’s pledge to free the party’s gathering from business and lobbyist support.

“The situation is a microcosm of a larger issue that Mr. Obama’s campaign has faced. It has tried to balance the president’s longtime pledge to reduce the influence of special interests in politics with his real-world need to raise the huge amounts of money that modern campaigns require, at times in ways that seem to contradict those pledges.”