With millions of television dollars and a week of intense personal campaigning, Illinois Sen. Barack Obama has worked to chip away at New York Sen. Hillary Rodham Clinton's lead among Pennsylvania Democrats.

All that effort has paid off -- or not -- depending on which poll you believe.

In surveys released yesterday, two established polling organizations with extensive experience in the state offered sharply contrasting readings of Mr. Obama's pursuit of Mrs. Clinton.

Quinnipiac University depicted a closing race, with Mr. Obama now within 6 percentage points of Mrs. Clinton. On the other hand, Survey USA, in a poll released by KDKA television, found Mrs. Clinton with a more comfortable lead of 56 percent to 38 percent -- or 18 percentage points.

The consensus of recent polls in the state is closer to the Quinnipiac finding, but there are outliers in both directions, including at least one that showed Mr. Obama with a slim lead.

Both candidates will be trying to move those numbers with new appearances in Pennsylvania today. Mrs. Clinton will court voters in Aliquippa, Beaver County. Mr. Obama will be on the other end of the state, in the battleground communities of suburban Philadelphia.

If Mr. Obama has narrowed the gap between the Democratic contenders, it would hardly be surprising, given his substantial advantage in money and television advertising in the first four weeks of the race here.

According to Evan Tracey, chief operating officer of CMAG Associates, a firm that tracks media spending, the Obama campaign has outspent its rival by a margin of nearly 4-to-1 so far. In an interview with the Associated Press, he said their spending, as of Sunday, was $3.6 million for Mr. Obama and $1.3 million for Mrs. Clinton.

Mr. Obama has spent roughly half of his money in the expensive Philadelphia media market, which covers the southeastern suburban communities that are seen as a key battleground in this contest. Mr. Tracey said Mr. Obama's financial advantage could be seen not just in the sheer volume of his advertising, but also in the types of shows -- including expensive prime-time programs -- during which his ads appear.

"The Clinton campaign has an 'American Idol' problem," Mr. Tracey said. "She isn't buying any. ... Obama is buying shows like 'American Idol,' 'CSI,' the very highest-cost programming available. It gets you all the voters, not just the older viewers you get with the news shows. That's an advantage."

The Clinton campaign announced yesterday that they would be airing a new round of commercials in the state, with one ad highlighting her family roots in the Scranton region, another emphasizing economic issues, two more showcasing her endorsements by Gov. Rendell and Philadelphia Mayor Michael Nutter and one targeting Hispanic voters.

How much the Clinton campaign will spend on the new ads isn't clear, although spokesman Howard Wolfson predicted in a conference call last month that the spending imbalance between the two rivals would shrink to perhaps 2-to-1 in the contest's closing weeks.

Mr. Obama, who had already been airing a Spanish-language commercial as part of his much-larger ad buy, has shown a series of mainly biographical spots so far. Seeking to appeal to women voters, a traditional source of support for Mrs. Clinton, the Obama campaign has released one new ad featuring his wife, sister and grandmother. Other new Obama ads include one focusing on energy independence and another using his late mother as the focus of a discussion of health care costs.

The tone of the two campaigns' ads, at least so far, has been milder than in some earlier states. Mrs. Clinton has aired a version of her now-famous 3 a.m. phone call ad in Pennsylvania, but its targets were the economy and Arizona Republican Sen. John McCain, the presumptive GOP nominee, rather than Mr. Obama.

Mrs. Clinton opened her Pennsylvania drive with a series of well-attended rallies across the state. She was back last week with several, mostly smaller events featuring round-table discussions with selected voters.

Mr. Obama's most extensive campaign foray came in a cross-state bus trip, in which he mixed town-hall style sessions with hand-shaking stops at sports bars, where he displayed his knowledge of basketball, and at a bowling alley, where he demonstrated that he's better off sticking to basketball.

The effects of their in-state campaigning were overshadowed by national controversies surrounding their campaigns. Mr. Obama was buffeted by attention to the incendiary sermons of his former pastor, the Rev. Jeremiah Wright -- a conflagration he addressed with his widely noted speech on race, delivered last month in Philadelphia. But to the Clinton campaign's dismay, the Wright issue got news-focus competition from Mrs. Clinton's since-recanted misstatements about arriving in Bosnia in 1996 under sniper fire.

In the campaign for Ohio, a state where Mrs. Clinton won handily, the Obama campaign tried to put her on the defensive over the North American Free Trade Agreement approved under her husband's administration. That assault was blunted by reports that an Obama economic adviser had told Canadian diplomats to discount the campaign trail rhetoric regarding the trade pact. But that table was soon turned as well.

Early last week, in speeches before Pennsylvania's AFL-CIO, both Democrats reiterated their opposition to a proposed free-trade agreement with Colombia. Two days later, the Wall Street Journal reported that Mrs. Clinton's chief strategist, Mark Penn, in his capacity has head of a lobbying firm, had met with Colombian officials to further pro-treaty efforts, even as his candidate was denouncing the pact.

Seeing a story with legs of its own, the Obama campaign at first declined to comment on the Penn matter, even after the Clinton camp announced that her strategist had been removed from his top post. But yesterday, the Obama forces tried to sharpen focus on the story via a conference call in which International Brotherhood of Teamsters President James Hoffa demanded Mr. Penn's complete ouster from her campaign.

In a television interview yesterday morning, Mrs. Clinton defended merely demoting Mr. Penn. "Contrast that to Senator Obama's campaign," she said, "where, as far as I know, nothing was ever done when one of his top economic advisers representing the campaign -- unlike Mr. Penn, who was not representing the campaign -- but Mr. Obama's representative told the Canadian government, basically, not to pay any attention to what Senator Obama was saying about NAFTA."

Together, the campaign developments revived the NAFTA issue in Pennsylvania -- a state that, like neighboring Ohio, has suffered extensive manufacturing job losses over the past decade.

The two Democrats share an essentially identical position on NAFTA now. Both say they would renegotiate the pact to strengthen its labor and environmental provisions. But the Obama campaign is never sorry to see the campaign dialogue focus on the pact's history rather than its future.

In today's appearances, both candidates will be stumping in areas of potential strength. Polls have shown Mrs. Clinton running strongly in Western Pennsylvania, in part because of her appeal to the older, blue-collar electorate of Beaver County. Mr. Obama will be in Pennsylvania's southeastern suburbs, a region that the new Quinnipiac poll shows as one of two regions of the state, along with Philadelphia itself, in which he is leading Mrs. Clinton.

Overall, that survey showed Mrs. Clinton ahead of Mr. Obama, with the support of 50 percent of likely Democratic voters to his 44 percent. A week, ago, the same organization put Mrs. Clinton's lead at 50 percent to his 41 percent. In the same survey in early February, Mrs. Clinton led by more than 20 points.

The latest version found Mrs. Clinton ahead in every area of the state except the Philadelphia media market. In Allegheny County, she was ahead, 57 percent to 39 percent. In Southwestern Pennsylvania, including Beaver County, her margin was even more impressive: 60 percent to 31 percent.

The Survey USA poll was looking at an apparently different contest, with Mrs. Clinton holding onto a strong lead of 56 percent to 38 percent. While comparing polls can be an apples-and oranges exercise, one apparent divergence between the two survey was that Survey USA found Mrs. Clinton leading in southeastern Pennsylvania, including Philadelphia, by a margin of 52 percent to 43 percent.

While the two polls identify regions somewhat differently, Quinnipiac's findings in the overlapping -- but not identical -- metropolitan Philadelphia region were, for the city, 55 percent for Mr. Obama and 37 percent for Mrs. Clinton, and, for the suburbs, 53 percent for him to 42 percent for her.

Both polls are among those included in the average of poll results maintained by the Website Pollster.com. Their average figure for the two candidates is 50.5 percent for Mrs. Clinton and 42.7 percent for Mr. Obama. A separate aggregation of polls by RealClearPolitics found a similar margin of 48.6 percent for her to 41.6 percent for him.