Sen. Hillary Clinton, D-N.Y., has won the Pennsylvania primary vote as expected with a decisive 10-point win.
The victory was "very big and very sweet," Clinton said today on ABC's "Good Morning America."
"Some people counted me out and said to drop out but the American people don't quit, and they deserve a president who doesn't quit, either," Clinton told supporters at a victory rally Tuesday night after walking out to Tom Petty's song "I Won't Back Down."
"We were up against a formidable opponent who outspent us 3-1... trying to knock us out of the race," Clinton said of Sen. Barack Obama, D-Ill. "Well the people of Pennsylvania had other ideas today."
Clinton told "GMA's" Diane Sawyer that the win should send a message to unpledged superdelegates.
"The road to the White House does go through Pennsylvania," she said, adding that Tuesday's win proves that she can win the large and swing states, crucial to a November victory.
But Clinton declined to endorse a call to let undecided superdelgates pledge to whoever wins the popular vote, where Obama still enjoys a half-million vote lead.
The pressure was on Clinton to win by a large margin and she delivered. With 99 percent of the precincts reporting, she won 55 percent of the vote, to Obama's 45 percent
Obama briefly congratulated Clinton in a speech in Evansville, Ind., but then turned to his common theme of the need for change in American politics and to attacks on Republican John McCain.
"After 14 long months, it's easy to forget this from time to time -- to lose sight of the fierce urgency of this moment," he said. "It's easy to get caught up in the distractions and the silliness and the tit-for-tat that consumes our politics; the bickering that none of us are immune to, and that trivializes the profound issues -- two wars, an economy in recession, a planet in peril -- issues that confront our nation."
Clinton's Pennsylvania victory fuels questions about why Obama hasn't been able to sew up the nomination, despite having more money, having won more states and having a lead in the popular vote and pledged delegates, according to ABC News' delegate scorecard.
With neither candidate able to get the 2,025 delegates needed to win the party's nomination, tonight's win in Pennsylvania will bolster Clinton's argument to superdelegates — the 795 Democratic party officials and members of Congress who may ultimately decide the nomination.
'Clear and Convincing Victory'
As the results pour in, pundits, Democratic superdelegates, and the media will characterize whether Clinton won by a large enough margin of victory. Devine and other Democrats have long argued the New York senator needed to win the Keystone State over Obama by double digits, and dig into Obama's delegate lead.
"If she wins by 10 points or more, it will be viewed as a clear and convincing victory, but if it's closer than that, it will be less than a clear and convincing victory," Democratic strategist Tad Devine said.
Speaking to reporters in Conshohocken, Pa., Tuesday, Clinton rejected that common argument, saying "a win is a win."
"But maybe I'm old fashioned about that. But you run a very competitive race at a considerable financial disadvantage. I think maybe the question ought to be why can't he close the deal?" she said. "Why can't he win a state like this one, if that is the way it turns out?"
Older, Blue-Collar Workers Key for Clinton
During the course of the Pennsylvania primary battle, the candidates went bowling and drank beer, with Clinton going one step further and downing shots of whiskey and appearing more comfortable at times than her opponent.
Obama garnered unwanted headlines after suggesting economic realities have left people in the state "bitter" and clinging to guns and religion. Obama later admitted he should have worded his thoughts better.
Clinton was expected to win in Pennsylvania in part because of her edge in past primaries among blue-collar workers, those without a college degree, and older voters — all demographics representative of the Keystone State. Obama, meanwhile, had hoped his hold on younger voters and high interest in this primary from a record 218,000 newly registered first-time voters would erode some of her support.
Clinton's Advantage in PA
"The state of Pennsylvania, on its face, given the nature of its voting population — older, white, Catholic, working class — for the most part, these are all demographic groups that Hillary Clinton has done well with throughout the course of this nominating process," Devine said.
Preliminary exit poll results indicate that nearly six in 10 Pennsylvania voters are women; under 50 percent of Pennsylvania Democratic voters have a college degree; three in 10 Democratic voters are Catholic; and almost half are liberals.
"To win this decisive, one candidate or the other, either Clinton or Obama, needs to break into the other candidate's base," Devine said.
If Obama bests Clinton in a state like Indiana or North Carolina where she is thought to have a strong base of support, Devine said, the race could shift in the Illinois senator's favor.
"If it doesn't, I think the race will continue the way it has since Super Tuesday, really, since Iowa and New Hampshire, just more of a see-saw than anything else, but one where Obama has been able to hold an advantage," Devine said.
Race To The End
Over a pancake breakfast at Pamela's Diner with his wife, Michelle, and owner of the Pittsburgh Steelers Dan Rooney, Obama said he doesn't expect the Democratic race to end until the last primary votes in June.
"I have come to the conclusion that this race will continue until the last primary or caucus vote is cast," Obama said. "And that's not far away."
Throughout the nominating process, Obama has done better than Clinton among young voters, urban voters, black voters and Democrats with college degrees.
As the polls opened in the Keystone State, both candidates got some last-minute jabs in on network and cable television interviews.
"I think there's a big burden on Sen. Obama... to prove that he can win a big state, because he hasn't really up until now," Clinton said in a pretaped interview with ABC's Chris Cuomo that aired on Tuesday's "GMA."
Clinton also decried Obama's fundraising advantage going into the state's primary. Obama outspent Clinton on TV in Pennsylvania by 2-1.
"I know very well that I'm in a real fight here," Clinton said. "Every time I turn around there are posters at bus stops and train trips and he's got an enormous cash advantage."
Obama had $42 million cash on hand in primary money by the end of March, according to his latest Federal Election Commission report. In comparison, Clinton had $9 million, but was carrying $10 million of debt. But Clinton told "GMA" today her campaign recieved $3 million in donations in the wake of Tuesday's win.
Early on Tuesday morning, Obama sought to manage expectations for any Clinton victory.
"Sen. Clinton started off with a big lead here. She had a 20-point lead," Obama told ABC's Robin Roberts on "GMA," "But we feel good about how we've chipped away at that lead."
A Quinnipiac University poll released Monday found Clinton with a seven-point edge on Obama in Pennsylvania. In mid-February, Clinton boasted a 14-point lead over Obama in Pennsylvania.
Negative TV Ads
The bitter Democratic battle turned even uglier in the lead up to the Pennsylvania primary, with the candidates launching negative ads and robotic calls against one another.
On Monday, Clinton launched an ad in Pennsylvania that questioned whether Obama is up to the task of being president in a time of crisis.
"Who do you think has what it takes?" the narrator asks over images of Osama bin Laden, headlines about the stock market crash of 1929, long gas lines from the 1970s oil-shocks and images of the Cold War, Hurricane Katrina and U.S. soldiers.
The ad quotes President Truman's famous line: "If you can't stand the heat, get out of the kitchen" — to cast Obama as complaining about last week's ABC News presidential debate.
The Obama campaign accused Clinton of using "scare tactics" in the ad. The Illinois senator's latest ad says: "Sen. Clinton has internalized a lot of the strategies, the tactics that have made Washington such a miserable place."
Defending his campaign's harsher tone, Obama told ABC News' Robin Roberts Tuesday: "You've always got to measure if somebody throws an elbow at you, and after three or four times of gettin' elbows in the ribs, you know, at what point do you sort of say, 'OK, you know, we, we, we've gotta put a stop to that?'" Obama said.
Both campaigns launched automated calls to Pennsylvania voters in a last-minute effort to question the credibility of their opponent, with Obama questioning Clinton's record on gun control and Clinton questioning Obama's record on energy.
Making headlines as voters go to the polls, former President Clinton told a Philadelphia radio station Monday that the Obama campaign took his Jesse Jackson comment and "twisted it for political purposes" and accused Obama's campaign of "playing the race card on me."
At the end of the interview, Clinton turned to an associate and said, "I don't think I should take any s-- from anybody on that, do you?"
"No, no, no, that's not what I said," Clinton told an NBC reporter. "You always follow me around and play these little games. And I am not going to play your games today. This is a day about election day, go back and see what the question was and what my answer was. You have mischaracterized it just to get a another cheap story to divert the American people from the real urgent issues before us, and I choose not to play your game today."
Taking on the GOP
Pennsylvania voters today chose between two bruised candidates after a grueling and nasty election fight.
Many Pennsylvania voters acknowledged the negative tone in the campaign, according to preliminary exit poll results. However Clinton is bearing the blame — two-thirds of Pennsylvania voters in preliminary exit poll results say Clinton attacked Obama unfairly; fewer, but still about half, also say Obama unfairly attacked Clinton.
While some party officials are wringing their hands about the bitter tone of the Democratic campaign, worried it will turn off independents and undecided voters and damage their chances against Sen. John McCain, R-Ariz., in the fall, others say despite the tone, voters mobilized to overturn eight years of the Bush administration and will rally behind either candidate if they win the nomination.
"A majority of Americans believe this country is headed off in the wrong direction," Devine said. "As long as [those] issues tend to dominate the electoral landscape, Democrats will have a real advantage."
ABC News' deputy political director Teddy Davis, Gary Langer, Nicole Gallagher, Sunlen Miller, Eloise Harper, Sarah Amos and Nitya Venkataraman contributed to this report.