Salena Zito

The nation's sixth most populous state, Pennsylvania bears many similarities to Ohio, where Clinton defeated Obama by 10 points Tuesday. It's a Rust Belt state largely abandoned by the once-mighty steel, coal and railroad industries.

"Look for lots of talk about NAFTA," Schaffner said.

Obama and Clinton have both said they want to re-evaluate and renegotiate the North American Free Trade Agreement, which became a contentious issue in the final days of the campaigns in Ohio and Texas.

Pennsylvania's comparatively high union membership -- 13.5 percent of state wage earners, compared to 12 percent nationally -- and large elderly population make it fertile ground for Clinton, whose political base is anchored by older white voters and blue-collar workers. The state AFL-CIO estimates a third of registered voters live in union households.

Clinton's daughter Chelsea campaigned for her mother in Philadelphia yesterday. The campaign was setting up a headquarters in Pittsburgh, operating out of a temporary office in the American Federation of State, County and Municipal Employees building Downtown.

Obama likely will not visit Pennsylvania until after Tuesday's primary in Mississippi.

"After that, expect to see him non-stop," said Obama spokesman Sean Smith.

Obama campaign workers have been meeting for training sessions and canvassing Pittsburgh neighborhoods in recent weeks. Hanna Spearman, 70, of Monroeville started volunteering about a month ago. She makes calls and does campaign research each day after waking up at 5 a.m.

She spent Wednesday afternoon with several other volunteers making calls on cell phones from Obama’s Pittsburgh headquarters in East Liberty. She spends about 6 hours a day calling people from there or trying to talk friends into voting Obama, she said.

"My friends are just sick of me because I talk about him every day. It’s just Barack Barack Barack," Spearman said. "I’m in love with him."

Clinton volunteers planned to start calling local residents last night after spending recent weeks making calls in Ohio and Texas. In the afternoon, workers were making campaign signs and talking about how to coordinate college voting groups.

Courtney Pellegrino, 43, of the South Side, traveled in recent weeks to volunteer for Clinton in Ohio.

"We have real problems here: job loss, lack of infrastructure, cost of gas, cost of food," said Pellegrino, who put up several signs outside Clinton's temporary headquarters on the Boulevard of the Allies. "I think she’s shown she can get results and has the skills to get her plans through."

Political observers expect Obama to do well in Philadelphia, the state's Democratic hub, where more than 40 percent of residents are black, and among the younger, better educated voters in the city's suburbs. Clinton, they say, might do better among more conservative, working-class Democrats in northeastern and southwestern Pennsylvania.

The state has a slim track record of electing women and blacks to public office -- relevant in a year when Democrats likely will have either the first female or first black nominee for president. Women comprise just 13 percent of the Legislature, in contrast to the national average of 23 percent. Blacks hold 8 percent of the seats, equal to the national average.

Most polls show Clinton leading in the state, but the margin has shrunk in recent weeks. A Quinnipiac University poll released last week showed Clinton with 49 percent of the vote and Obama with 43 percent.

Because Democrats mete out delegates proportionately, it is unlikely that either candidate will gain much ground in the battle for Pennsylvania's 187 delegates.

Despite her wins Tuesday, Clinton picked up just 12 delegates out of about 370 at stake, according to The Associated Press.

Obama's overall delegate lead stood at 1,566 to 1,462 as he and Clinton looked ahead to the final dozen contests on the calendar. It takes 2,025 to win the nomination, and neither candidate is likely to reach that milestone with the other still in the race.

So both campaigns are intensely lobbying party leaders, the superdelegates who attend the convention but are not chosen in primaries or caucuses.

About 350 of them remain uncommitted, enough to swing the nomination. Those who have endorsed a particular candidate can change their minds.

Salena Zito

Salena Zito is a political analyst, reporter and columnist.