The core group also includes Gregory B. Craig, a former top official in the Clinton State Department who served as the president’s lawyer during his impeachment trial; Richard J. Danzig, a Navy secretary in the Clinton administration; Mark W. Lippert, Mr. Obama’s former Senate foreign policy adviser, who just returned from a Navy tour of duty in Iraq; and Mr. McDonough.

Mr. McDonough and Mr. Lippert are paid by the campaign and based in Chicago, and the rest are outside advisers who volunteer their time from Washington.

The group no longer includes Samantha Power, the Pulitzer Prize-winning Harvard human rights expert who resigned in March after she was quoted calling Mrs. Clinton a “monster.” But Mr. Lake still talks to Ms. Power, and Mr. Obama sent a long personal tribute that was read at her wedding in Ireland this month.

Mr. Obama’s Republican rival, Senator John McCain of Arizona, has a far smaller and looser foreign policy advisory operation, about 75 people in all, and none are organized into teams. In 2004, the Democratic presidential nominee, Senator John Kerry, had a foreign policy structure similar in scale to Mr. Obama’s, but it had limited influence on the candidate, who had spent 20 years in the Senate, former advisers said. Mr. Obama is not yet receiving the government intelligence briefing that is typically made available to a presidential candidate upon becoming his party’s nominee.

Mr. Obama’s infrastructure funnels hundreds of e-mail messages and reams of position papers and talking points each day to members of the core group, who in turn seek advice or make requests for more information to team members down the line. Dennis Ross, the Middle East envoy for Mr. Clinton and the first President Bush and a member of the Obama campaign’s Middle East team, is frequently asked by Ms. Rice, Mr. Lake or Mr. McDonough for help on framing Mr. Obama’s comments on Iran’s nuclear program and its potential threat to Israel.

“They’ve asked for substantive help: ‘Can I take a look at language on Iran?’ ” Mr. Ross said. “Or sometimes I’ve been asked questions to explain the administration’s approach on Iran.” Mr. Ross participated in a conference call last week with Mr. Obama and other advisers to prepare for the senator’s foreign trip, and he will travel with Mr. Obama in Israel and the West Bank city of Ramallah and at other stops. Mr. Ross described Mr. Obama in the conference call as focused on “drilling down” into the issues on the trip.

Another person who has contributed outside advice is former Secretary of State Colin L. Powell, whom Mr. Obama has been wooing. Mr. Powell, a Republican, has a friendship of decades with Mr. McCain, but friends say he has felt excluded from Mr. McCain’s foreign policy operation and was impressed when Mr. Obama called on him in June. Mr. Powell also met around the same time with Mr. McCain.