ST. PAUL, Minn.

Coming off a bumpy convention that was postponed by a hurricane 1,000 miles to the south and set unpleasantly abuzz by a teen pregnancy 2,000 miles to the north and west, Republican presidential nominee John McCain now faces the task of convincing voters that his rock solid political experience trumps Democrat Barack Obama's rock star atmospherics.

"McCain's not going to compete with Obama on eloquence. He's not even going to try," said Newt Gingrich, the former House Speaker. "McCain is going to compete on common sense, on being Harry Truman to Obama's Tom Dewey."

Whether that posture as the Republican Truman will sell to voters could depend on his ability to negotiate the transition from maverick outsider to standard bearer of an incumbent party in which he is sometimes viewed as the house renegade.

With a pair of speeches -- running mate Sarah Palin's Thursday night and Mr. McCain's last night -- the candidate signaled that he is ready to embrace the conservative wing of his party and its rhetoric. As such, the spontaneity that long allowed Mr. McCain to charm small gatherings is likely to give way to a more scripted, strategically crafted approach.

Mr. McCain, who once referred to the press as his constituency, has largely broken off the free-wheeling media gaggles at which he dispensed his plain talk, partly because the gaggle has turned into a mob and partly to keep a sometimes overly discursive candidate on message. Handlers spent a bad week dealing with the backlash on a simple McCain goof: Asked how many homes he owned, the candidate, married to a wealthy heiress, was unable to answer.

"After you're the presidential nominee, the world changes," said Sen. Lamar Alexander, R-Tenn., himself a former presidential hopeful, in 1996. "As much as possible he needs to still find a way to be himself. I know in '96 they shut Bob Dole up and one of Bob Dole's endearing characteristics was his sense of humor and without that sense of humor he wasn't the Bob Dole everyone knew."

Faced with less informality and the need to keep his words guarded, Mr. McCain now needs to stress the more prosaic specifics of governance, a task in which his supporters think he can surpass Mr. Obama, but which are often hard to turn into voter excitement.

"He needs to turn the corner now and really relate to the American people," said former House Speaker Dennis Hastert. "He needs to get our fiscal house in order, what he's going to do on banking. And then, how he's going to reach out and help the American family -- I think those are really the issues that people want to see.

"You're not going to compete with being a rock star. John McCain is substance and Barack Obama is a rock star."

So far, independent observers worry that Mr. McCain's campaign has lacked focus, with his stands on various issues largely known, but still incoherent in the sense of what policy directions a McCain presidency would take.

"It's like the sum of the parts don't give us the whole," said G. Terry Madonna, a political analyst at Franklin and Marshall College in Lancaster.

While moving to define himself, Mr. McCain must perform a task faced by virtually every candidate for office in a media-driven age, say party activists: Define his opponent as well.

"All we have to say is ... they're the left," said Mr. Gingrich, whose confrontational partisanship helped turn the House Republican in 1994, a political watershed for his party. "We're for lower taxes, they're for higher taxes. We're for conservative judges, they're for liberal judges. Not much harsh about it."

He predicted that a clearer definition of Mr. Obama as a liberal would likely give the McCain-Palin ticket a majority of moderate, blue-collar Clinton voters in Pennsylvania, Kentucky and West Virginia. Republican leaders here spent much of the week touting Mr. Obama as the single most liberal senator in Washington.

But while defining Mr. Obama might be part of the equation, the collateral task for Mr. McCain is to also brand himself as a comfortably familiar political entity, according to John Brabender, a Pittsburgh consultant who has run numerous GOP campaigns and who has been doing work for the Republican National Convention.

Mr. McCain "doesn't have to move voters into the unfavorable category, he just has to move them into the questionable category where they go into the voting booth feeling Obama doesn't have the experience needed for the presidency," Mr. Brabender said.

He likened it to a soft-drink marketing strategy, comparing Coca-Cola to an off-brand energy drink.

"Every time you take a sip of coke, you pretty much know what it's going to taste like. Barack Obama is a little like one of these new energy drinks with all the caffeine in it. The packaging looks really cool, but in due time there might be some questions about whether you should be drinking that stuff," Mr. Brabender said.

That tagging of Mr. Obama as a celebrity -- one of the harshest ads from the McCain camp compared the Democrat to Britney Spears and Paris Hilton -- is the likely prelude to the selling of Mr. McCain as a comfortable, established brand.

Robert Mosbacher, the former commerce secretary who is now general chairman of the McCain campaign, said turning Mr. Obama's celebrity against him has given the McCain forces a chance to turn their own man's lack of glitz into a strength.

"I was worried about it when we did it," Mr. Mosbacher said. "But when they tagged Obama with being a celebrity and a rock star, it stuck because it's true.

"He is. He's a rock star. Look at him -- 200,000 people in Germany. Young people who haven't done anything before. Yeah, he's going to appeal to that. But I think the people when they do some sober, specific thinking aren't really going to want to take a chance on something like that."