Mr. McCain’s battle of Lexington is part of a struggle he is engaged in every day. A politician who has thrived in the give-and-take settings of campaign buses, late-night TV couches and town meetings, he now is trying to meet the more formal speaking demands of a general election campaign.

By his own admission, Mr. McCain is not a great orator. He is ill-suited to lecterns, which often dwarf his small stature, and he tends to sound as if he is reading his lines, not speaking them. His shortcomings have been accentuated in a two-man race, particularly because the other man  Senator Barack Obama, the presumptive Democratic nominee  can often dazzle on stage.

Mr. McCain and his advisers know that Mr. Obama’s ability to excite huge crowds will make for an inevitable podium mismatch for the older, softer-spoken Republican. “We’re going up against a guy who is off the charts,” said Mark Salter, Mr. McCain’s longtime Senate chief of staff and campaign adviser.

To better compete, Mr. McCain is undergoing a subtle but marked transition as a political performer, said aides and people who have watched him. As part of a staff shakeup that was announced Tuesday, he brought in a new adviser  Greg Jenkins, a former White House official and Fox News producer  who will oversee the producing and staging of Mr. McCain’s events. Mr. Jenkins is considered an expert at political stagecraft, oversaw many of President Bush’s appearances and served as executive director of the 2004 inaugural committee.

Mr. McCain is working closely with aides like Brett O’Donnell, a former debate consultant for Mr. Bush, to improve his speech and performance. He is working to limit his verbal tangents and nonverbal tics. He is speaking less out of the sides of his mouth, which can produce a wiseguy twang reminiscent of the Penguin from the Batman stories, and he is relying less on his favorite semantic crutch  the phrase “my friends”  which he used repeatedly in his campaign appearances. He also appears to be trying to exercise restraint, advisers and campaign observers say, when speaking off the cuff, wisecracking in town meetings and criticizing his opponent. In recent weeks, for example, Mr. McCain seems to have reined in the sarcasm he has directed at Mr. Obama. (In May, for example, he said of his opponent, “With his very, very great lack of experience and knowledge of the issues, he’s been very successful.”)