Conservatives around Mr. McCain counter that the other side’s concerns are groundless because Mr. McCain is hardly an empty vessel who might succumb to the views of one group or another.

“I would say his world view is so established that there is not a real battle going on,” said Mr. Kagan, a scholar at the Carnegie Endowment for International Peace. “A struggle over individual policies I could imagine, but the broad view, no. People would agree on what McCain thinks. This is not one of those situations like Bush all over again, with some titanic struggle going on between different factions.”

Mr. McCain’s advisers say he talks to realists like former Secretary of State Henry A. Kissinger and former Secretary of State George P. Shultz. Mr. Kissinger said in an interview that he had talked with Mr. McCain “15 to 20 times in the last year,” including on a bus ride to a fund-raiser on Long Island.

“In his speeches and daily pronouncements, I generally have no input,” Mr. Kissinger said. “When we meet for lunch or dinner, or on the one or two occasions he has come to my home, we have had philosophical discussions. When he calls me now, it will be mostly ‘this event has happened and what do you think?’ ”

Mark Salter, one of Mr. McCain’s closest advisers, called the concerns of the pragmatists “utter nonsense” and added that “if John McCain on a given issue would talk to Bob Kagan about 30 percent as often as he talks to Henry Kissinger, for some people that is 30 percent too much.”

Although the concerns at this point are focused more on access to Mr. McCain than on major policy differences, there have been some substantive areas of dispute. Mr. Kissinger was said to have been disturbed by Mr. McCain’s hardline attitude on Russia and the Russian president Vladimir Putin in the March 26 speech, viewing it as “going far beyond anything that is necessary” and “something that he has got to be talked out of,” according to someone who has spoken recently with Mr. Kissinger.

“I have no comment on that paragraph,” Mr. Kissinger said when asked directly. “You have to take my judgment from what I have written. But I am a strong supporter of the senator.”