The new numbers come as the parties and allied groups are pouring fresh cash into the close race.
With 10 days left before the Nov. 6 election, the question is: Does the oncoming Smith still have a chance to catch Casey, or will the incumbent hold him off?
The Inquirer's team of national pollsters, one a Republican and one a Democrat, agreed that the race has yet to be decided. They differed on the likelihood of Smith's pulling it out.
"Time is not on Mr. Smith's side," said Jefrey Pollock, president of Global Strategy Group, a Democratic survey firm. "If Mr. Smith wants to go to Washington, he's got to make his move in coming days."
"But the race is close," he said, "and it's not over."
Adam Geller, chief executive of the Republican polling firm National Research Inc., said: "Right now, there is nothing in the numbers that tells me Smith has topped out. . . . My guess would be that Smith still has more juice to squeeze out of this."
The pollsters said that, as campaign days grow fewer, the contest becomes less about persuading voters and more about psyching them up to vote.
In that regard, Casey and Smith could be hostage to the candidates at the top of the ballot, President Obama and Mitt Romney. The Inquirer poll found Obama ahead in the Keystone State by six points, down from eight in the previous survey.
Casey's poll profile in Pennsylvania is like Obama's in many ways. Both are doing well among women, but struggling with men. Both fall short of the 50 percent-plus needed to cement a win.
Claudia Utti, a grandmother from Lafayette Hill in Montgomery County, who participated in the poll, said there was "just something" about Smith she didn't like.
"I just don't have a good feeling about him," she said Friday in a follow-up interview. "Casey's OK - I'm not overwhelmed, but I would vote for him."
William Kuchinsky, a pro-Smith businessman from West Chester, said: "I guess my problem with Casey is that he is a lifelong politician. . . . I just think at this point our country needs people who have had actual experience outside of Washington, or outside of state government."
Periodic Inquirer polls since August show the impact of the $15 million that Smith has spent on TV advertising, much of it painting Casey as "Senator Zero."
Fifty percent of voters viewed Casey favorably in August, and 43 percent did so early this month. Just 38 percent do now, the latest poll found.
Smith's favorable rating, by contrast, has risen - from 19 percent, to 29, to 34 percent.
A large number of voters still have no strong opinion of either man.
Pollock, the Democratic pollster, said the hopeful news for Casey was that he seemed to have stanched Smith's gains in the huge Philadelphia media market.
Smith has been flooding the region with TV ads since summer; Casey only started airing his commercials in the region Oct. 1.
"I think there is no doubt," Pollock said, "when you look at Philadelphia and the Philadelphia media market that the numbers have stabilized."
The hopeful news for Smith, Republican pollster Geller said, is that a majority of undecided voters typically go for the challenger in almost any race.
"We are seeing generally that they lean a little bit Republican," Geller said.
Recent polls in the Senate race have varied widely. Pollock said this followed a trend nationally this year.
The Democratic Senatorial Campaign Committee said Friday that it had a poll showing Casey rebounding to a 12-point lead, 52 percent to 40 percent.
A Rasmussen Reports survey released Friday gave Casey just a one-point lead - a statistical tie.
A recent poll by Muhlenberg College had Casey up by eight; a Quinnipiac University survey put him ahead by three.
With the likely result so much in flux, independent and national party groups, for the first time, have begun to weigh in.
An unnamed official at the National Republican Senatorial Committee told the Washington Post on Friday that the group was giving $500,000 in coordinated funds to Smith.
Majority PAC, a pro-Democratic group, has stepped in with ads to help Casey, the Associated Press reported. And a group called Fight for the Dream PAC was buying airtime for ads to help Smith.
Contact Tom Infield
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