Hempstead, New York (CNN) - Hours before the second presidential debate Tuesday, a new poll indicates a close contest between President Barack Obama and Republican nominee Mitt Romney for Pennsylvania's 20 electoral votes.
According to a Quinnipiac University survey released Tuesday morning, 50% of likely voters in the Keystone State say they are backing the president, with 46% supporting Romney. Obama's four point advantage is within the poll's sampling error.
The Quinnipiac survey is the second straight poll in 24 hours to indicate Obama with a four point edge in Pennsylvania. A Muhlenberg College poll released Monday had Obama at 49% and Romney at 45% among likely voters in the state.
It was a different story last month, prior to the first presidential debate. The president had a 12 point lead over the former Massachusetts governor in Quinnipiac's late September poll. And he had a seven point advantage in Muhlenberg's survey and a nine point lead in a poll from Franklin and Marshall.
The new Quinnipiac poll indicates the gender gap continues, with Obama up 19 points among women and Romney ahead by nine points among men. According to the survey, Romney has a 13 point lead among white Catholic voters.
"Gov. Mitt Romney is coming on strong in the Keystone State, especially among white Catholics," said Tim Malloy, assistant director of the Quinnipiac University Polling Institute.
By a 42%-37% margin, the poll indicates Pennsylvania-born Vice President Joe Biden won last week's debate over Rep. Paul Ryan of Wisconsin, the GOP running mate. But more than six in ten say the vice presidential showdown doesn't affect their vote for the White House.
"Pennsylvania voters say Vice President Joseph Biden, a native son and a Catholic, won the debate and is more qualified than U.S. Rep. Paul Ryan to be president. But that doesn't seem to be lifting the top of the ticket," Malloy said.
George H.W. Bush's 1988 victory in the state was the last time a Republican carried Pennsylvania in a presidential election. But the state remained competitive in the resulting cycles, until four years ago, when then-Sen. Obama eventually ended up carrying Pennsylvania by 10 points over Sen. John McCain. But two years ago, the GOP enjoyed a strong showing in the midterm elections, winning back the governor's office, a Senate seat and five House seats from the Democrats.
In the state's U.S. Senate race, the survey indicates Democratic incumbent Sen. Robert Casey Jr. with the support of 48% of likely voters and Republican challenger Tom Smith, a businessman, at 45%.
The Quinnipiac University poll was conducted October 12-14, with 1,519 likely voters in Pennsylvania questioned by telephone. The survey's sampling error is plus or minus 2.5 percentage points.