PHILADELPHIA, Pennsylvania (CNN) -- Sens. Hillary Clinton and Barack Obama are preparing for their face-off in Pennsylvania -- where the demographics appear to play in Clinton's favor and voters might be less receptive to Obama's message of "change."
Sen. Hillary Clinton lags behind Sen. Barack Obama in the popular vote and in pledged delegates.
"Two million residents over the age of 65 ... a very heavily unionized state ... a lot of Catholics in this state ... women in Pennsylvania vote at a higher rate than men in Pennsylvania," said John Baer of the Philadelphia Daily News.
Clinton also has family roots in Pennsylvania. Her father, Hugh Rodham, was the son of a factory worker from Scranton, according to the Clinton campaign.
Obama's emphasis on change might not be on the forefront of voters' minds in Pennsylvania.
More than three-quarters of the people who live in Pennsylvania were born there.
"It speaks to a state where change isn't an important element in day-to-day life," Baer said.
And pollster Terry Madonna points out -- Pennsylvania's makeup resembles places that have been good to Clinton. Watch more on Pennsylvania's Democratic voters »
"The eastern part of Pennsylvania is more like New Jersey, and the western part is more like Ohio, and she won both of them," Madonna said.
The question now: Does Obama have a chance in the state?
"The only way that Sen. Obama can do better than losing this state by 5 to 8 percent is if he is able to capture the imagination of new voters," Baer said.
Strategists say Obama could win Pennsylvania the same way Gov. Ed Rendell beat Bob Casey in the 2002 Democratic gubernatorial primary -- by sweeping Philadelphia and its suburbs.
There's only one problem: Rendell has endorsed Clinton and is working hard to deliver his state for her.
Clinton's strongest argument for her nomination is that she can win states such as Pennsylvania. Watch more on the upcoming contests »
"I've won the big states. I've won the states that a Democrat has to win," she has said. Watch Clinton discuss the economy in Pennsylvania »
That argument disappears if she loses Pennsylvania.
"I think that would effectively end her campaign," Madonna said.
Harry VanSickle, commissioner of the state's Bureau of Commissions, Elections and Legislation, told CNN Radio this week that the state had a little more than 4 million registered Democrats and 3.2 million Republicans eligible for the April 22 primaries.
Monday was the deadline to sign up to vote in the primary.
A resident must be a registered Democrat to vote in the Democratic primary, where 158 delegates are at stake.
VanSickle noted Pennsylvania had 8.2 million total registered voters at the time. The math shows 49 percent of Pennsylvania voters were registered Democrats as of Monday, compared with 39 percent for Republicans.
The primary registration numbers will not be final until later in the week, as officials accept mail-in forms postmarked by Monday.
The executive director of Philadelphia's Republican City Committee says the Democratic primary has hit his city like a hurricane.
"There appear to be tens of thousands of new registered Democrats in Philadelphia County. We're not sure exactly, you know, where they came from or why they haven't shown up on the radar before," said Alan Schmidt. E-mail to a friend
CNN Radio correspondent Lisa Desjardins contributed to this report.