Washington - Senator Hillary Clinton's advantage over Barack Obama has narrowed among voters in Pennsylvania, the next major prize in the heated state-by-state contest for the Democratic presidential nomination, a poll showed Wednesday. Clinton out-polled Obama 50 per cent to 41 per cent among likely primary voters in the north-eastern state's April 22 vote, down from a 53-41 lead in a survey two weeks ago, the Quinnipiac University poll said.
Analysts see a major win in Pennsylvania - the last large state yet to vote in the intra-party race - as key for Clinton, who trails Obama in the number of delegates needed to secure the nomination at the party convention in August.
An average of polls calculated by the website RealClearPolitics over two weeks shows Clinton with just a 6-percentage-point lead over Obama, after she held a significant double-digit lead previously.
Obama won the backing Wednesday of Lee Hamilton, a leading Democratic authority on foreign policy who headed the commission that investigated the terrorist attacks of September 11, 2001.
Hamilton is a former congressman from Indiana, where polling shows Obama and Clinton running neck-and-neck in the states own presidential primary in May.
Hamilton called Obama "pragmatic, visionary and tough" in an interview with Bloomberg News.
Obama's inroads in Pennsylvania came after he picked up the endorsement last week of the state's popular Senator Bob Casey. Clinton has long held the edge among influential Pennsylvania politicians with early endorsements from Governor Ed Rendell and the Democratic mayors of both Philadelphia and Pittsburgh.
The former first lady holds a clear lead with Pennsylvania's female voters but is tied with Obama among Democratic men, the Quinnipiac poll said. Obama has an advantage among younger voters, but Clinton leads 54 per cent to 37 per cent among the state's large older population.
"Her strength is her clear advantage among white voters - blue collar whites, less educated whites, economically hurting whites, that group known famously as Reagan Democrats," Clay Richards, assistant director of the university's Polling Institute, said in a statement.
"Obama is marshalling all his forces, but despite his eloquent dialogue on the race issue, Pennsylvania Democrats are unmoved. So far."
The economy, the Iraq war and health care are voters' top issues, the poll showed.
The survey of 1,550 likely Democratic voters has a margin of error of 2.5 per cent.
Qunnipiac University is in the north-eastern state of Connecticut.
