Campuses in the cities and mountainsides are alive with political activism, stirred most notably by Obama in student registration drives aimed at replicating his success with young voters dating to the Iowa caucus in January.
How motivated are his youthful supporters? So motivated that Alyssa Beasley, 20, endured an encounter with the DMV so she could switch her driver's license from New Jersey and register to vote at the same time.
And how high are their expectations? In Beasley's case, very.
"I feel like my entire hope and dream for America lies on this man's shoulders," she said on the tree-lined campus of the Jesuit-run University of Scranton.
That heady courtship is matched by a vigorous effort on Clinton's side. Altogether, the April 22 primary is becoming more of a can't-miss event for the young instead of just another why-bother one on the political calendar.
Doug Jones, 19, got so caught up in the excitement that he registered as a Democrat to vote for Clinton, even though he'll probably vote Republican in the fall.
"I'm not doing it out of sneaky and scheming motives to down the Democratic nominee," said the University of Scranton student. "I'd like to take part in the process."
Pennsylvania ranks third in the nation in the percentage of people 65 and older, a group that has favored Clinton elsewhere and appears strong for her here.
Obama is counting on a big showing from the state's nearly 700,000 college students on more than 150 campuses.
The Illinois senator has received the support of about 60 percent of voters aged 18-24 in competitive states, exit polls indicate, and his advantage with that group doesn't appear to be waning in Pennsylvania.
The question is whether that will be enough to prevail in a state where polls have found Clinton consistently ahead, if by shrinking margins.
"We have a long way to go in Pennsylvania and maximizing the votes of young voters is critical if we're going to be able to close the gap," said Sean Smith, an Obama spokesman.
Pennsylvania makes voting easy for students from other states because it only requires 30 days residency to register. However, no one who voted in an earlier primary elsewhere can vote again here.
Mia Prensky, 21, of Harrisburg, said Obama supporters have been on her campus at Bryn Mawr College - a women's school with stone buildings nestled in Philadelphia's wealthy Main Line - handing out stickers, distributing information about the Iraq war and encouraging students to vote. They struck a chord with her.
"I still don't really like the fact that Hillary voted for the war," she said.
In Philadelphia, where more than 100,000 college students live, Obama volunteers with voter registration forms in hand have been on campuses and at train stations around Philadelphia's bustling University City district, encouraging their peers to register.
Among them was Seth Dean, 23, a University of Pennsylvania student who said he decided in January to register as a Democrat in Pennsylvania. At home in Florida, he was a registered independent.
"I kind of thought from the beginning it was going to be kind of a long, drawn-out fight and it might come down to Pennsylvania, so I just made a tactical decision," Dean said.
Aside from Obama's strong base among black voters, young voters are probably his strongest group, said Scott Keeter, director of survey research for the Pew Research Center.
"I cannot recall another candidate in the past couple of decades that had such consistent support from young people," Keeter said.
A recent Quinnipiac University poll found Obama leading Clinton 51 percent to 42 percent among likely Democratic voters ages 18-44 in Pennsylvania, but trailing nine points overall.
Obama's campaign ran an ad in Pittsburgh and Harrisburg before the state's March 24 registration deadline aimed at drumming up new young voters. It cited his opposition to the Iraq war and his plan to help loan-burdened college students.
Additional efforts by Obama to reach young voters in Pennsylvania include a text messaging program that allows supporters to communicate with each other and receive information about events, said Sean Smith, a campaign spokesman.
Facebook co-creator Chris Hughes has been in the state training people how to use the social networking site for outreach, Smith said. In all, the campaign has more than 50 student chapters in Pennsylvania.
During a recent Obama rally at Penn State University in State College, more than 20,000 people crowded onto a campus lawn to see him, many of them students wrapped in blankets against the cold.
Clinton's campaign also is after younger voters with registration drives, rallies and about 30 student groups. "Ugly Betty" star America Ferrera is among celebrities who have campaigned in Pennsylvania for Clinton, as has the New York senator's daughter, Chelsea.
The campaign says it is reaching young people who are not in college as well as students.
One of them is Ashley Langdon, 23, a waitress in Allentown who said she would like to go to college but can't afford it. Langdon said she's hypoglycemic and has struggled to pay emergency room bills because she doesn't have health insurance.
"She has the experience and the knowledge to help clean it up a little bit better, rather than Obama," Langdon said of Clinton.
"He's kind of new. He's fresh. He's got outstanding ideas, but who knows what's going to happen?"
More than 235,000 people have registered as Democrats in Pennsylvania since last year. State authorities estimate nearly 10 percent of the 4 million registered Democrats are ages 18-24 and about 20 percent are 65 or older.
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