Sen. Hillary Rodham Clinton will come to Pennsylvania's hard coal country tomorrow, kicking off her campaign in a state where a victory is essential to maintain her newfound momentum.

After an appearance in Scranton tomorrow, Mrs. Clinton will head to Harrisburg and Philadelphia on Tuesday, six weeks before a primary in which history and demographics are on her side. .

"It's hers to lose," said Rep. Mike Doyle, D-Forest Hills, a superdelegate who is neutral in the Democratic battle.

Sen. Barack Obama is also expected to campaign in the east early in the week. And by the time of the April 22 balloting, no part of the state is likely to be a stranger to either of the Democratic rivals.

"If they voted right now, she would win, I don't think there's any question about it," said Rep. Jason Altmire, D-McCandless, another neutral superdelegate. "But what we've seen from Sen. Obama in the past is that when he campaigns he can make up ground. ... He has time to change that dynamic.''

Mr. Altmire noted that his district, which starts at the Ohio border and carves an irregular arc north of Pittsburgh, has 125,000 residents over 65 and roughly 65,000 veterans.

"Those are groups that have generally supported her,'' he said.

Senior aides to the Democratic rivals seem to share the two superdelegates' assessments.

"Undeniably, this is a state where Sen. Clinton has huge advantages,'' David Plouffe, Mr. Obama's campaign manager, said of Pennsylvania.

"We think Pennsylvania is absolutely critical to this campaign,'' said Howard Wolfson, Mrs. Clinton's press secretary. "I believe both campaigns believe that, Both campaigns are going to be sending hundreds of staff. ... We feel very good about our prospects in Pennsylvania."

The lessons of the race that just took place to the west bolster the case for Mrs. Clinton. In Ohio, she followed her pattern of doing well with a number of groups, including older voters and Catholics. Pennsylvania remains the second oldest state in the nation and the anthracite region she'll visit Monday is one of the older parts of the state.

In an interview posted on the Web site of the Pew Forum on Religious Life, John Green, an expert on religion and politics, noted some of the omens for Pennsylvania in the Ohio returns.

"In the Buckeye State, the exit polls showed her winning about two-thirds of white Catholics. Clinton also did well with white Protestants in Ohio, winning two-thirds. Although the evidence is fragmentary, it appears that Clinton won both the white mainline and evangelical Protestant vote," he said.

Mr. Green noted that Pennsylvania, "is a state with a religious demography a lot like Ohio."

Catholics represent about 21 percent of the population in Ohio, but 29 percent in Pennsylvania. And their share of the Democratic primary vote would be expected to be even greater.

Sen. Bob Casey, who says he doesn't plan to pick a candidate until after the primary, said that the issues terrain in Pennsylvania will also resemble Ohio's.

"The two candidates will have to talk about health care, the subprime crisis. ... The trade issue is going to be an issue in a way that's similar to Ohio," he said. "There's a lot of places in Pennsylvania that have been devastated in the last decade."

Leo Gerard, president of the United Steelworkers, highlighted the trade issue in a conference call with reporters last week.

"It's fundamental that there be a new dialogue on trade that leads to a new consensus on trade and how we negotiate any future trading agreements or review any existing trade agreements," Mr. Gerard said in the conference call, which was arranged by Public Citizen, a consumer group skeptical of recent trade accords.

"I appreciate that the leading Democratic candidates had a spirited discussion about NAFTA, but the fact of the matter is you can't fix NAFTA by putting in environmental rights and labor rights and pretending that that will fix it ... We need to change the whole discussion about investment, about subsidy, about enforcement of trade laws."

Mr. Gerard's union had endorsed former North Carolina Sen. John Edwards before he dropped out of the race. The USW is currently neutral in the Democratic contest.

Mr. Casey suggested that the turnout rates across the state could dramatically shape the results. Mr. Obama faces a more promising demographic picture in Philadelphia and its surrounding suburbs. The city has the state's highest concentration of African-Americans. Its suburban ring includes many of the more affluent and better educated Democrats who have gravitated to Mr. Obama in earlier contests.

Mr. Casey pointed out that the Philadelphia media market has accounted for a shifting proportion of the state's total vote in recent primaries. In most years, he said, the Philadelphia region's percentage of the state's Democrats was in the mid-30s, but in 2000, when he lost the gubernatorial primary to Ed Rendell, the Philadelphia region produced roughly 45 percent of the primary total.

But it is not certain which candidate would benefit from a disproportionate Eastern Pennsylvania turnout. While some of the demographic factors would seem to play to Mr. Obama's advantage, Mrs. Clinton has the advantage of high-profile support from Michael Nutter, Philadelphia's newly elected mayor, and most significantly, from Mr. Rendell, who is hugely popular not just in his former city but in its surrounding suburbs and the nearby Lehigh Valley .

"[Mr. Rendell] is a huge asset," said Mr. Casey. "The impact of any endorsement depends on how active the person is. When he endorses someone, he only has one speed -- all out.''

The ties between Mr. Rendell and the Clintons go way back. Mr. Clinton appointed Mr. Rendell as general chairman of the Democratic National Committee during his second term. In that post, Mr. Rendell helped raise millions for the Democratic Party while making contacts that allowed him to enhance his already prodigious fund-raising ability. Mr. Clinton also appointed Mr. Rendell's wife, Marjorie, to the U.S. 2nd Circuit Court of Appeals.

Mr. Casey's father, Bob Casey Sr., who served two terms as governor, had a rougher relationship with President Clinton. He blamed the former president for banishing him from a speaking role at the 1992 convention. Sen. Casey, however, praised both of the Democratic contenders, pointing out that both had campaigned for him in his 2006 victory over Sen. Rick Santorum.

"In terms of 1992, there's no question there was a mistake made there, but she wasn't president," he said. "Sen. Clinton is a colleague of mine, we've worked together on health care ... on pre-K education. I sit on the Foreign Relations Committee with Sen. Obama."

Mr. Casey said he planned to maintain his neutrality because he believes that he and other senior Democrats will be called on to help unify the party after the extended, fractious nominating battle.

"When I look at this campaign, not just as a senator but as a citizen, someone who's interested in electing a Democrat, I want to make sure we don't just win. We want to have a candidate with a real mandate.''