Polls close in latest Democratic vote

VOTING ended in Pennsylvania on Tuesday in the increasingly nasty Democratic battle between Hillary Clinton and Barack Obama, with Clinton hunting a convincing win that would keep her White House hopes alive.

Results were not immediately available in Pennsylvania, where Clinton was favored but needed a substantial victory to gain ground on Obama and convince party leaders she would be the best candidate to face Republican John McCain in November's presidential election.

Her one-time 20-point lead over Obama in the state slipped to single digits in many polls amid an onslaught of advertisements by Obama, who outspent her 2-to-1 in the first nominating contest in six weeks.

Both camps tried to play down expectations before the vote.

"This was always an uphill climb but what we feel is that we've made significant progress," Obama said at a diner in Pittsburgh. "A lot of it is going to depend on turnout today and it's really hard to gauge."

A record number of Pennsylvanians are registered to vote and turnout was heavy at many polling places, local media said.

Exit polls showed Clinton won about 58 percent of those who made their choice in the last week. Obama was on the defensive over a series of campaign controversies in a Philadelphia debate last week, and Clinton questioned his toughness in an ad on Monday featuring images of al Qaeda leader Osama bin Laden.

Voters also were not happy with the race's negative tone. About two-thirds of Pennsylvania voters thought Clinton unfairly attacked Obama, while about half thought Obama had unfairly attacked Clinton, the polls showed.

The Pennsylvania vote opens the final phase of the Democrats' hard-fought duel for the nomination. Nine more contests are scheduled before the campaign voting ends on June 3.