Clinton lead narrows in Pennsylvania poll

NEW YORK (Reuters) - Democratic presidential candidate Hillary Clinton leads rival Barack Obama by six percentage points in Pennsylvania, down from 16 points two weeks earlier, according to a Quinnipiac University poll released on Wednesday.

The final two Democratic contenders face off in Pennsylvania's April 22 primary, which could prove significant if the race for the Democratic nomination in the November election is still close.

Following March 4 primaries in Texas and in Ohio, Pennsylvania is the biggest state left on the state-by-state election calendar.

The Pennsylvania poll, conducted February 21-25, showed Clinton, a New York senator, with a lead of 49 to 43 percent among likely Democratic voters. A previous Quinnipiac poll, conducted February 6-12, showed her with a lead of 52 to 36 percent.

The biggest shift in preference was detected among younger voters, aged 18 to 44, who went from 52 to 41 percent in favor of Clinton in the earlier poll. They moved to 58 to 41 percent in favor of Obama, an Illinois senator, in the more recent poll, Quinnipiac said.

"If Senator Clinton survives next week (in Texas and Ohio) to fight another day, Pennsylvania could become the last battleground of the long Democratic contest. But an Obama win in Texas and Ohio would make it difficult for Clinton to halt her rival's momentum," Clay Richards, assistant director of the Quinnipiac University Polling Institute, said in a statement.

The poll surveyed 506 likely Democratic primary voters and had a margin of error of plus or minus 4.4 percentage points.

Quinnipiac also surveyed 1,872 Pennsylvania voters who favored either Clinton or Obama over the leading Republican candidate, Arizona Sen. John McCain.

Clinton led McCain in a hypothetical match-up by 44 to 42 percent in Pennsylvania while Obama led McCain 42 to 40 percent. That poll had a margin or error of plus or minus 2.3 percentage points.

(Reporting by Daniel Trotta, Editing by Ellen Wulfhorst and David Wiessler)