A new poll finds modest improvements in the re-election prospects of both Gov. Ed Rendell and U.S. Sen. Rick Santorum, although the Republican senator still lags well behind his prospective challenger, state Treasurer Bob Casey Jr.

A Quinnipiac University survey released yesterday also found continuing weakness in President Bush's job-approval rating among Pennsylvania voters, coupled with a strong though slightly reduced majority of voters who said that going to war in Iraq was the wrong thing to do.

In trial heats against potential 2006 opponents, Mr. Rendell ran well ahead of his Republican rivals, and his approval rating rebounded from earlier surveys. While other responses continued to suggest potential vulnerability for the Democratic incumbents, his opponents have yet to capitalize on them.

In the survey, 48 percent said they approved of Mr. Santorum's performance in office while 38 percent disapproved and the balance were undecided. Forty-five percent said that Mr. Santorum deserved to be re-elected and 40 percent said he did not.

In both categories, Mr. Santorum's latest findings were slightly improved from an October Quinnipiac poll and about on par with his numbers from earlier in the year.

Mr. Santorum also made a slight dent in the commanding lead Mr. Casey has held in earlier polls. In the Dec. 13 survey, Mr. Casey led Mr. Santorum by 50 percent to 38 percent, a 12-point margin that was slimmer than the 52 percent to 34 percent result found by an October Quinnipiac poll.

Those results come after several weeks in which a third-party conservative group, Americans for Job Security, which is officially unrelated to the Santorum campaign, had aired roughly $1 million worth of ads lauding Mr. Santorum's record on Social Security. By a margin of more than two-to-one, the voters said that the senator's re-election chances were hurt by his support for the president.

One of the most provocative, if hypothetical, findings of the poll involved Mr. Casey's potential vulnerability on the abortion issue. Respondents who said they would vote for Mr. Casey and who said they were pro-choice were reminded that the Democrat, like Mr. Santorum, is opposed to abortion; 22 percent said that they would not vote in the election, while 6 percent said they would vote for another candidate.

That suggests opportunities for Mr. Santorum to suppress the Casey vote. It also points to the possibility that a credible pro-choice third-party candidate in November could significantly alter political terrain that now seems to favor the Democrat.

In the governor's race, Mr. Rendell continues to run ahead of his GOP challengers and appears to have come through the state pay raise controversy in much better shape than the members of the Legislature.

A majority, 51 percent, said they approved of Mr. Rendell's job performance while 13 percent disapproved. That represented a reversal of the modest dip in approval margins the Democrat had experienced earlier in the year.

Mr. Rendell's popularity continued to vary sharply by region. The former Philadelphia mayor remained hugely popular in the eastern part of the state, but ran behind the levels a Democrat would expect to record in the southwest. In Allegheny County, the margin in favor of Mr. Rendell was just 49 percent to 41 percent, and in the neighboring counties of the southwest, his disapproval rating, at 47 percent, was well ahead of his 35 percent approval rating.

In head-to-head match-ups, the incumbent ran ahead of the leading Republicans, former Lt. Gov. William Scranton and ABC broadcaster Lynn Swann, by nearly identical margins of 48 percent to 36 percent and 35 percent, respectively.

Mr. Swann enjoyed a lead among the registered Republicans surveyed, but all of the GOP contenders trailed "don't know," in a match-up of the contenders for the GOP nomination.

The GOP figures were Mr. Swann, 31 percent; Mr. Scranton, 23 percent; state Sen. Jeff Piccola, 5 percent; and James Panyard, 2 percent.

The Quinnipiac findings were based on phone interviews with 1,447 Pennsylvania voters; the poll had a margin of error of 2.6 percent.

The subsample of 633 Republican voters had a margin of error of 3.9 percent