Mr. McCain methodically dismissed as unrealistic every other plan that had been proposed by Democrats as a substitute for President Bush?s strategy, including those from Senators Hillary Rodham Clinton of New York, Joseph R. Biden Jr. of Delaware and Barack Obama of Illinois.

He said that if the Bush administration?s plan had not produced visible signs of progress by the time a McCain presidency began, he might be forced ? if only by the will of public opinion ? to end American involvement in Iraq.

?I do believe that history shows us Americans will not continue to support an overseas engagement involving the loss of American lives for an unlimited period of time unless they see some success,? he added. ?And then, when they run out of patience, they will demand that we get out.?