Mr. Obama had said he quit smoking at the beginning of his campaign for president, in early 2007. But he later admitted to having “bummed” cigarettes from others, and last week he told Barbara Walters that he had “fallen off the wagon.”

On Sunday, Mr. Brokaw pressed Mr. Obama as to whether he had actually quit.

“What I would say is, is that — that I have done a terrific job, under the circumstances, of making myself much healthier,” Mr. Obama replied, suggesting that he had at least cut back while running for the most high-pressure job in the world.

As for whether he might break the ban on smoking at 1600 Pennsylvania Avenue, Mr. Obama said that “I think that you will not see any violations of these rules in the White House.” (Like a good politician, he left some wiggle room, not making an outright commitment to quit for good, suggesting merely that he would not smoke in the Executive Mansion.)

The campaign’s ad this week comparing Obama to Paris Hilton and Britney Spears, though attracting criticism from Democrats, got heavy play on the Internet and in print and TV media.

The campaign reportedly is spending $140,000 a day to run the ad in battleground states, and aides are echoing its content in daily talking points.

“We’re running against a celebrity. He is someone who gathered throngs of fans overseas,” McCain spokesman Tucker Bounds told FOX News Saturday.

And after Obama’s campaign announced Saturday it would accept three presidential debates with McCain — and not the kind of town hall meetings McCain had wanted — McCain spokesman Brian Rogers again invoked the comparison.

“We understand it might be beneath a worldwide celebrity of Barack Obama’s magnitude to appear at town hall meetings … but we hope he’ll reconsider,” he said in a statement.

McCain has struggled to stick with one label for Obama, casting him as a pessimist, a liberal and more recently a flip-flopper.

But aides say the flip-flopper charge has not stuck in the minds of voters, and that the campaign will instead continue to define Obama as an inexperienced celeb.

The campaign even tried to mockingly compare him to Moses in an ad released Friday.

McCain told reporters at the time his campaign is just “having some fun” and showing a “sense of humor.”

But that might not be all he has in mind. After Obama spoke to more than 200,000 spectators at his rally last month in Berlin and held high-level meetings recently with members of the Bush administration and foreign leaders, the McCain campaign is driving home the message that Obama is being too presumptuous.

It’s unclear what impact the gambit will have on the polls in the long term, but the Gallup daily tracking poll Saturday showed Obama and McCain tied at 44 percent for the second day in a row. That’s after Obama had opened up a 9-percentage-point lead a week ago.

The McCain campaign even balked at an opportunity to bring back the flip-flopper charge Saturday, after Obama told a Florida newspaper he would support a compromise plan in Congress to allow some offshore oil drilling, which he’s long opposed.

“This wasn’t really a new position,” Obama told reporters.

And the McCain campaign agreed.

They circulated Obama’s claim and sent out their own statement saying: “We hope Barack Obama will realize that his ongoing opposition to John McCain’s realistic energy solutions and additional off shore drilling is wrong.”

Granted, McCain was the first to reverse course and support offshore oil drilling. But his campaign also seemed to drop a charge that Obama was playing the race card. That charge was leveled earlier in the week after Obama told a group of Missouri voters that Republicans would try to make voters afraid of him because he doesn’t look like past presidents.

McCain said Friday he did not bring up the issue, that Obama did, and now he wants to “move on.”

Obama said Saturday he doesn’t think McCain is racist, only cynical. And he ridiculed McCain for the celebrity ads.

“You’ve got statistics that say we’ve lost another 50,000 jobs, that Florida is in a recession for the first time in a decade and a half and what was being talked about was Paris and Britney,” Obama said.

“They’re clever on creating distractions from the issues that really matter in people’s lives,” he said. “We’ve got to make sure we keep focused on people’s day-to-day concerns. We don’t take the skill of the Republicans in engaging in negative campaigning lightly.”

Clinton did just that at a stop Saturday at Bronko’s restaurant in Crown Point, Ind.

The two presidential candidates continued to hammer each other Monday after a weekend of criticism stemming from Obama’s comment that some small-town voters are bitter over their economic circumstances and “cling to guns and religion” as a result. Obama uttered the words at a private fundraiser in San Francisco last week and Clinton has seized on them in seeking the edge in Pennsylvania, which holds its primary April 22.

Obama also chided Clinton over NAFTA and the Colombian trade deal. Clinton has criticized NAFTA, which was passed under her husband’s watch. She opposes the Colombian trade deal even though former President Clinton supports it and her top campaign strategist, Mark Penn, met with Colombian officials to help push for its passage. Penn has since been demoted.

“Here’s what you can’t do. You can’t spend the better part of two decades campaigning for NAFTA and PNTR for China, and then come here to Pennsylvania, and tell the steelworkers you’ve been with them all along,” Obama said. “You can’t say you are opposed to the Colombia Trade deal, while your key strategist is working for the Colombian government to get the deal passed.”

Clinton was scheduled to address the gathering later Monday. Both candidates are hoping to secure the endorsement of the influential United Steelworkers union, which backed Democrat John Edwards before he dropped out of the race. Steelworkers president Leo Gerard introduced Obama to the crowd, saying, “We’re tired, we’re frustrated, we’re angry and we need somebody who’s going to stand up for fair trade.”

Campaigning Sunday in Pennsylvania, Clinton derided Obama’s comments about small-town voters as “elitist and divisive” and suggested they could doom Democrats’ chances for recapturing the White House in November if Obama were the nominee.

At a union hall outside Harrisburg, Obama said he’d expected blowback from GOP nominee-in-waiting John McCain but said he’d been “a little disappointed” to be criticized by Clinton. “Shame on her,” he said.

Laughing, the Illinois senator noted Clinton seemed much more interested in guns since he made his comments than she had been in the past. On Saturday, the former first lady reminisced about learning to shoot on summer vacations in Scranton, where her father grew up.

“She is running around talking about how this is an insult to sportsmen, how she values the Second Amendment. She’s talking like she’s Annie Oakley,” Obama said.

Clinton has told campaign audiences that she supports the rights of hunters. She’s also said she once shot a duck in Arkansas, where she served as first lady.

Clinton, who is trailing Obama in the popular vote and pledged delegates, has pounded Obama since audio from his San Francisco appearance was posted on The Huffington Post Web site. She hoped the comments might give her a new opening to court working-class Democrats less than 10 days before the Pennsylvania primary, which she needs win to keep her campaign going.

At the San Francisco fundraiser, Obama tried to explain his troubles in winning over some blue-collar voters, saying they have become frustrated with economic conditions: “It’s not surprising, then, they get bitter, they cling to guns or religion or antipathy to people who aren’t like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations.”

In Scranton on Sunday, Clinton said Obama’s words would probably alienate voters in Pennsylvania and other states holding primaries in the coming weeks. Indiana and North Carolina vote on May 6.

“How does he see people here in this neighborhood, throughout Pennsylvania, Indiana, North Carolina, other places in our country?” she asked during an informal news conference. “I think that’s what people are looking for, some explanation, and he has simply not provided one.”

“People don’t vote on economic issues because they don’t expect anybody is going to help them,” Obama told a crowd at a Terre Haute, Ind., high school Friday evening. “So people end up voting on issues like guns and are they going to have the right to bear arms. They vote on issues like gay marriage. They take refuge in their faith and their community, and their family, and the things they can count on. But they don’t believe they can count on Washington.”

The Huffington Post Web site reported Friday that Obama, speaking of some Pennsylvanians’ economic anxieties, told supporters at the San Francisco fundraiser: “You go into these small towns in Pennsylvania and, like a lot of small towns in the Midwest, the jobs have been gone now for 25 years. … And it’s not surprising then they get bitter, they cling to guns or religion or antipathy to people who aren’t like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations.”

In Terre Haute, Obama said he did describe some voters as bitter when a donor asked why working-class voters in Pennsylvania were not getting behind his campaign.

“Well, that’s not my experience,” Clinton told a Drexel University crowd, describing the state’s residents as resilient, optimistic and hardworking.

“Pennsylvanians don’t need a president who looks down on them,” she said. “They need a president who stands up for them.”

Steve Schmidt, a spokesman for Republican candidate John McCain, described Obama’s comments as “condescending” and “out of touch.”

In Terre Haute, Obama chided McCain for not responding promptly to the home mortgage crisis and criticized Clinton for voting for a bankruptcy bill supported by credit card companies.

“No, I’m IN touch,” he said. “I know exactly what’s going on. People are fed up, they are angry, they’re frustrated and they’re bitter. And they want to see a change in Washington.”

Clinton spokesman Phil Singer said Friday night, “Instead of apologizing for offending small-town America, Senator Obama chose to repeat and embrace the comments he made earlier this week.”

Tucker Bounds, a spokesman for McCain, said Friday: “Only an elitist would say that people vote their values only out of frustration. … You can’t be more out of touch than that.”

“Obama has won more delegates, he’s won more votes, he’s raised more money, and now you see it happening with superdelegates too,” said Simon Rosenberg, head of the Democratic advocacy group NDN.

Neither Obama nor Clinton is likely to win enough pledged delegates in state contests to clinch the hard-fought battle for the Democratic presidential nomination, leaving superdelegates to decide the race. The Democratic nominee will face Republican John McCain in the November election.

Despite heavy courting by Clinton, most of the superdelegates who made up their minds since January backed Obama. Clinton’s superdelegate lead dwindled to about 30 from 100 in that time.

A count by MSNBC gives Clinton 256 superdelegates to Obama’s 225. Obama, an Illinois senator, has gained steam in the past month, winning more than two dozen new commitments, compared with a handful for Clinton, a New York senator.

“It has been a drip, drip, drip toward Obama,” said Steven Schier, a political analyst at Carleton College in Minnesota.

“Superdelegates can see Obama’s advantages growing, and it’s pretty clear it’s going to be very hard for Clinton to catch him,” he said. “If Obama notches a few more victories, it could become a stampede.”

Obama has suggested that superdelegates back the candidate with the most pledged delegates — he leads by about 130 — and popular votes. He leads Clinton by about 700,000 votes, excluding contests in Florida and Michigan that were not sanctioned by the national party.

Clinton has struggled to overtake Obama in the Democratic contest and has rejected calls from some Obama supporters to get out of the race.

More than 300 superdelegates remain uncommitted or have yet to be named, giving the candidate who wins the bulk of them a path to the nomination.

CLINTON TRIES TO CLOSE GAP

Clinton hopes a strong run in the last 10 contests starting April 22 in Pennsylvania will close the gap with Obama in pledged delegates and popular votes, bolstering her claim she is best suited to beating McCain.

The private battle for superdelegates has been as tough as the public campaign for votes, with both camps courting uncommitted party leaders and trying to keep supporters in line.

Clinton has suffered high-profile reversals like the decision by U.S. Rep. John Lewis of Georgia, a prominent black supporter, to switch to Obama. Another superdelegate ally, New Jersey Gov. Jon Corzine, suggested that backing a candidate who did not win the popular vote “would be a hard argument to make.”

But she recently won the support of U.S. Rep. John Murtha of Pennsylvania and picked up three more superdelegates this week.

“Most superdelegates are in a holding pattern. They’re waiting to see what happens in Pennsylvania and down the road before they make any decisions,” Clinton spokesman Phil Singer said.

Rosenberg said the recent string of superdelegate endorsements for Obama made that argument hard to swallow. “A substantial number have moved — and most are moving to Obama,” he said.

Wayne Holland, chairman of the Utah Democratic Party and a superdelegate, endorsed Obama on Thursday. He said he thought Obama could help Democratic candidates throughout Utah and the West by attracting new voters, donors and volunteers.

“As state chair, my job is to try to elect as many Democrats in various offices in this state as possible,” he said. “I was looking for who could best help us win here, and that was overwhelmingly Senator Obama.”