WASHINGTON (CNN) -- Sen. Barack Obama continues to chip away at Sen. Hillary Clinton's lead in the crucial state of Pennsylvania, a new Quinnipiac poll out Tuesday showed.
Sen. Barack Obama appears to be closing the gap with Sen. Hillary Clinton in Pennsylvania, polls say.
The New York senator's lead over Obama now stands at 6 points in the new poll, 50-44 percent.
That compares to the 9-point lead Clinton held in a similar survey released five days ago, and an 11-point lead in a Quinnipiac survey late last month.
Specifically, Clinton has lost ground among white voters and men: She now holds an 18-point lead among whites, down from a 25-point gap in last week's poll, and trails Obama by 4 points among males.
Last week, the two drew equal support from men.
But Clinton continues to remain strong with her core voting bloc of older voters and white women, and likely Pennsylvania Democratic voters rate her more favorably than Obama -- 71 percent for Clinton and 67 percent for Obama. Watch how the Keystone State could shake up presidential race »
The latest Quinnipiac poll and CNN's poll of polls released on Monday show Clinton's lead over Obama in Pennsylvania continues to shrink ahead of the state's April 22 primary.
Monday's polls, conducted March 26 through Saturday, showed Clinton holding a 7 percentage point lead over Obama -- 49 percent to 42 percent; 9 percent remained unsure.
That gap is 4 percentage points narrower than a similar CNN poll of polls conducted March 26 through Wednesday. In that average, Clinton led the senator from Illinois 51 percent to 40 percent. Nine percent also were unsure then. Watch more on the polls »
The most recent poll of polls consists of three surveys: American Research Group (April 5-6), Muhlenberg College (March 27-April 2) and Quinnipiac (March 24-31). A sampling error for the poll of polls can not be calculated.
What's behind the shift?
"Obama has outspent Hillary Clinton three to one just on television advertising in Pennsylvania. He spent more than $3 million trying to get his name out and his message out to Hillary Clinton's $1 million," said Mark Preston, CNN's political editor.
The Illinois senator has also heavily benefited from the Service Employees International Union, which according to recently filed FEC reports has spent well over $700,000 on get-out-the-vote-efforts there. Watch more of Obama campaigning in Pennsylvania »
Clinton, however, has traditionally done well with working class voters, a group with considerable influence in the upcoming primary. Watch developments in the Democratic primary race »
Political observers point out that polls are not votes, and there's still a lot of time for anything to happen as the two Democrats battle it out for delegates.
According to the latest CNN count, Obama has 1,629 delegates, with 1,414 pledged delegates and 215 superdelegates, according to the latest CNN count.
Clinton has 1,486 delegates, with 1,243 pledged delegates and 243 superdelegates.
A total of 2,024 delegates is needed to win the Democratic nomination. It's unlikely either candidate will win the necessary delegates before the national convention in August. E-mail to a friend
CNN's Dan Lothian, Alexander Mooney and Alan Silverleib contributed to this report.