The poll shows Obama leading Romney 49 percent to 45 percent among likely voters with 4 percent undecided. Obama's lead is down 5 percentage points from last month.
Two third-party presidential candidates, Green Party nominee Jill Stein and Libertarian Party nominee Gary Johnson, barely register with voters in the poll.
The poll also shows U.S. Sen. Bob Casey Jr. leading Republican opponent Tom Smith, 46 percent to 36 percent, among likely voters with 13 percent undecided.
Obama's campaign is focused on a well-tuned ground game turning out three voter groups crucial to his re-election: Women, young people and minorities.
The poll shows Obama running strong with those groups - winning 54 percent of women, 55 percent of voters aged 18-34 and 73 percent of nonwhite voters.
"For Romney, the key is to cut down the president's edge among women while holding his edge with men," pollster G. Terry Madonna said Tuesday.
Romney's camp is touting a stronger effort in Pennsylvania with absentee ballots this year than U.S. Sen. John McCain had as the GOP nominee in 2008.
There was some good news for Romney in the poll - more people thought he was prepared to deal with economic problems than Obama. That's the predominant issue in this race.
Obama dominates in vote-rich Philadelphia, with 79 percent of the support, but Romney is in a virtual tie for the surrounding suburban counties.
Romney's campaign said on Tuesday that he would start televising ads this week in Pennsylvania criticizing Obama's record on regulating the coal industry.
Obama's campaign on Monday said he too would start running ads this week in Pennsylvania.
Both campaigns refused to provide details of when those ads would air or for how long.
Two pro-Romney political-action committees, Restore our Future and Americans for Job Security, launched TV ads this week in Pennsylvania, criticizing Obama's economic efforts.
Romney's campaign on Tuesday sent reporters a memo citing comments made last week by former Gov. Ed Rendell, who said a "startling upset" was possible in Pennsylvania this year.
The memo left out the portion of Rendell's comments where he said that could happen if Democratic voter "turnout collapses."
Rendell fired back Tuesday with a statement from the Obama campaign saying that Romney's new TV ad in Pennsylvania is a sign of "desperation."
"This is part of the old Republican playbook," Rendell said. "They tried a last-ditch attempt to expand the electoral base in 2008 when they were losing Ohio, Iowa, Florida and other traditional battleground states."
Pennsylvania has 20 Electoral College votes. A Republican presidential candidate has not won the state since then-Vice President George H.W. Bush in 1988.
Contact Chris Brennan at email@example.com or 215-854-5973. Follow him on Twitter @ChrisBrennanDN. Read his blog at phillyclout.com.