By BETH FOUHY and LIZ SIDOTI
Associated Press Writers
PHILADELPHIA (AP) - A six-week, increasingly caustic Pennsylvania primary contest between Democrats Hillary Rodham Clinton and Barack Obama culminated Tuesday as voters registered their choice - a decision that could save or sink Clinton's flagging candidacy.
The candidates questioned each other's character and readiness to be commander in chief in last-minute television ads and barnstormed the state in a final pitch for votes in the most populous and delegate-rich state remaining in the nominating contest. Some 4 million Democrats were eligible to cast ballots, with 158 delegates at stake.
Clinton was relying on a decisive win to reinvigorate her candidacy, while Obama hoped for an upset or a strong enough finish to secure the delegates needed to maintain his overall lead.
Late polling showed Clinton with a single-digit lead in the state after besting Obama by 20 points or more in earlier surveys.
As the polls opened at 7 a.m., the candidates engaged in a last round of sparring in pre-taped interviews aired on network and cable television.
"What (Obama) has to demonstrate is to win a big state, a big state that Democrats need to win in order to achieve the presidency," Clinton told CBS' "The Early Show." "The road to Pennsylvania Avenue for a Democrat goes right through Pennsylvania."
Obama, noting Clinton's polling lead, sought to lower expectations both in TV interviews and as he greeted the breakfast crowd at a Pittsburgh diner.
"We think we've made enormous progress" though "it's an uphill battle," Obama said. He noted that polls show a tighter race than just a few weeks ago but said: "We still, I think, have to consider ourselves the underdog."
"We've got a great organization. A lot of it's going to depended on turnout," Obama added.
Sarah Triplett arrived to vote Tuesday long before her suburban Philadelphia polling place opened and soon had plenty of company.
"I had to be here to vote, and I pray that Obama does make a big change in a very positive way," said Triplett, a "65-plus" woman from Levittown who works with the disabled.
In Allentown, where a line snaked out the door at First Presbyterian Church, 68-year-old Ellen Woolley, who works in finance, went for Clinton. Obama, she said, is a "marvelous speaker, but I really don't hear a lot of substance."
The issue of race in the campaign was renewed when former President Clinton, asked in an interview broadcast Tuesday with Philadelphia radio station WHYY about comments he made before the South Carolina primary, said the Obama campaign "played the race card on me."
"And we now know, from memos from the campaign and everything, that they planned to do it all along," Bill Clinton said.
Asked about Clinton's remarks, Obama chuckled and said: "So, former President Clinton dismissed my victory in South Carolina as being similiar to Jesse Jackson, and he's suggesting that somehow I had something to do with it? Ok, well, you'd better ask him what he meant by that. I have no idea what he meant. These were words that came out of his mouth, not words that came out of mine."
Obama and his wife, Michelle, addressed a rally at the University Pittsburgh on Monday night. They were joined by Teresa Heinz Kerry, wife of 2004 Democratic nominee John Kerry.
Heinz Kerry noted that her husband carried Pennsylvania in the general election. "I'm asking you to keep this streak going," she said.
In Philadelphia, Clinton appeared with her husband and their daughter, Chelsea, before a crowd at the University of Pennsylvania.
"It's not enough to say 'Yes we can.' We have to say how we can," Clinton told the crowd, putting a twist on Obama's popular slogan of hope.
The Pennsylvania contest turned sharply negative in its closing days as Obama cast doubts on his rival's honesty and trustworthiness. Clinton, in turn, questioned whether Obama was tough enough for the rigors of the Oval Office.
The campaigns tangled Monday over a new Clinton television ad that invoked images of Osama bin Laden - the first time a Democratic candidate has used the mastermind of the Sept. 11, 2001, terrorist attacks in the 2008 race for the White House.
"Harry Truman said it best, 'If you can't stand the heat, get out of the kitchen.' Who do you think has what it takes?" the ad says, as a picture of bin Laden and other national emergencies - from Hurricane Katrina to the fall of the Berlin Wall - flash on the screen.
The Obama campaign moved quickly to counter the message, airing a response ad within hours that challenged Clinton's 2002 vote authorizing the U.S. invasion of Iraq.
Obama addressed the matter himself at the Pittsburgh rally.
"My job as commander in chief is to keep you safe. That will be my number one task," adding, "The war in Iraq was unwise."
Pennsylvania's demographics suit Clinton. The state has a higher median age, a higher percentage of whites, a lower median household income and fewer bachelor's degrees than the country overall. These are the voters - working-class whites and voters older than 50 - who have flocked to her in past contests.
The Republican primary is also being held Tuesday, but Sen. John McCain of Arizona is already the certain nominee.
Liz Sidoti reported from Pittsburgh.
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