WASHINGTON—Hillary Clinton beat rival Barack Obama in a do-or-die showdown in Pennsylvania on Tuesday, according to a Fox network projection, prolonging the Democratic presidential race and keeping alive her White House hopes.
Clinton's margin of victory over Obama was still unclear. She was aiming for a substantial win that would help her narrow Obama's lead in delegates who select the Democratic nominee at the August convention.
The New York senator's one-time 20-point lead over Obama in Pennsylvania had slipped to single digits in many polls amid an advertising onslaught by Obama, who outspent her 2-to-1 in the first Democratic nominating contest in six weeks.
The vote opened the final phase of the hard-fought Democratic duel for the right to face Republican John McCain in November's presidential election. Nine more contests are scheduled before the voting ends on June 3.
Both camps had tried to play down expectations before the vote.
"A win is a win," Clinton said in Conshohocken, a Philadelphia suburb, before the polls closed. She noted Obama's heavy spending. "I think a win under these circumstances is a terrific accomplishment," she told reporters.
Turnout was heavy at many polling places, and a record number of Pennsylvanians had registered to vote.
Exit polls showed Clinton won about 58 percent of those who decided in the last week. Obama was on the defensive over a series of campaign controversies in a debate last week, and Clinton questioned his toughness in an ad featuring images of al Qaeda leader Osama bin Laden.
Obama has a nearly insurmountable lead in popular votes won during the first three months of the primary battle and in delegates. But neither can clinch the nomination without the help of superdelegates—nearly 800 party insiders who are free to support either candidate.
Clinton hopes a big win in Pennsylvania ignites a strong run through the last nine contests, convincing superdelegates she is the candidate who can capture the big states that will be crucial in November.