MEDIA, Pa. (AP) - To bisect the heart of the Democratic presidential contest, take the Chester exit of I-95 and wend your way to the Pennsylvania Turnpike. If Barack Obama has any chance of cultivating an upset on April 22, this 20-mile stretch is fertile land.
These are Philadelphia's western suburbs - a patchwork of charming small towns, elite colleges and working class neighborhoods that constitute one of the most competitive political battlegrounds in the state.
"It is, without question, right at the center of the fight for Pennsylvania," said Rep Joe Sestak, D-Pa., the retired admiral who represents this district and who has endorsed Obama's rival, Sen. Hillary Rodham Clinton. "How my district goes is how the state may go."
Clinton holds a lead in statewide polls. But Obama is strongly favored in Philadelphia and polls show him holding a slight lead in the arc of four increasingly Democratic counties around the city. Delaware County, the one which makes up most of Sestak's 7th congressional district, is his toughest with demographics that also suit Clinton and her blue collar appeal.
"She has experience and we need something," said Stacey Martinez, a 30-year-old graphic designer, as she stood outside her row house in the inner suburbs near the city line. "The economy stinks. We need something new. When Bill Clinton was in the White House, we didn't have these problems and maybe she had something to do with it behind the scenes."
To the west is Media, the county seat. With its Internet-wired coffee shops, quaint storefronts and local progressive politics, the borough's Democrats are more typical of Obama supporters.
"It's nice to be inspired by a politician," said Andrew Arata, the 34-year old owner of Earth & State, an arts and crafts shop in the center of town. Arata, who switched his registration from Independent to Democrat so he could vote for Obama, said he also feared the emergence of White House family dynasties.
"Since I started voting, it's been a Clinton or a Bush," he said.
Martinez and Arata were among two dozen Delaware County voters interviewed randomly by The Associated Press this week.
For Obama, who leads in the number of delegates needed to secure the nomination, a victory here would pierce Clinton's claim that he can't win primaries in large states. A Clinton victory would buttress her argument to stay in the race to the end. But even if the Southeast Pennsylvania counties don't propel Obama to victory, their concentration of delegates has driven the candidates and their surrogates to lavish attention on this corner of the state.
In Delaware County alone, Clinton made a surprise visit to Martinez' working class Drexel Hill neighborhood on Sunday, was in Haverford College with her daughter, Chelsea, on Thursday and planned to campaign with Sestak in Radnor on Friday.
Obama has consistently stayed ahead of Clinton in advertising in the state, spending about $7 million statewide to her $2.7 million, according to Evan Tracey, of TNS Media Intelligence/Campaign Media Analysis Group, a political ad tracking firm. But in the expensive Philadelphia media market, Tracey said, Clinton has caught up to Obama in broadcast ads and both are at parity.
Obama backers see hope in Democratic Gov. Ed Rendell's gubernatorial primary victory in 2002. Then, Rendell, a Philadelphian, carried the eight counties in the Philadelphia media market by a 4-1 margin. He only won two of the remaining 59 counties in the state, but it was enough to beat Democrat Robert Casey, now a U.S. senator.
"Sen. Obama can do the same thing, but needs to do better than the polls show him doing in the suburban counties," said Anthony Campisi, the first vice chair of the Delaware County Democratic Party and an Obama supporter. "The polls show him in the low 50s. To build a big enough margin to carry the state his percentage needs to increase close to 55-60 percent."
Short of a win, Obama-backing strategists are looking to secure enough delegates to blunt Clinton's likely success statewide. Seven of the state's 19 congressional districts yield 50 of the state's 103 elected delegates. All but one of those districts are concentrated in and around Philadelphia.
The 2nd Congressional District in Philadelphia has nine delegates at stake. To win six of them, Obama would have to win the district with 62 percent of the vote. Sestak's 7th Congressional District has seven delegates; to win five of them Obama would need more than 64 percent of the vote.
Those are tall orders. Rendell and Philadelphia's popular mayor, Michael Nutter, are backing Clinton. Earlier this week, a poll by the Quinnipiac University Polling Institute, showed that Obama barely led Clinton by two percentage points in the suburbs after having enjoyed an 11 point lead the week before.
And Delaware County, something of a lynchpin in the calculation, has mixed allegiances. There are 11 colleges or universities in Sestak's congressional district. The students and the upscale educated Democratic voters who live in the outer developments and old stone houses are part of Obama's core support. But the district has one of the highest percentages of residents with Irish ancestry - a Catholic concentration that together with blue collar workers and the elderly form a solid base for Clinton.
Clinton benefits from a fondness for her husband among many voters.
"I know that when Bill Clinton was in office, the economy was good, we weren't at war and I think he'll be helping her in some fashion with the Cabinet. So I'm leaning to Hillary right now," said Robert Thomas, a 30-year-old general manager of a convenience store.
Joe Kernen, waiting for his commuter train into Philadelphia at a station in Swarthmore, Pa., said he is supporting Clinton for "her experience as a senator, her intelligence and precision on the issues."
Still, polls show as much as 12 percent of voters in the Pennsylvania primary remain undecided. Asim Maqbool, a physician who teaches pediatrics at Children's Hospital in Philadelphia, spoke for many when he described his ambivalence.
"What impresses me most about Hillary is she has a number of facts and figures at her disposal. She's obviously been immersed in this sort of work on a different level than Sen. Obama," he said. But he spoke admiringly of Obama as a candidate who exudes optimism and vision.
"When you look at people like Barack Obama, he's more of a transformational candidate," he said. "Is this going to be his year? I don't know."