A new survey depicts a static Pennsylvania electoral picture with the Democratic candidates maintaining their double-digit leads in the races for governor and U.S. Senate.

The survey of 1,200 voters by Strategic Vision, a Republican consulting and public affairs firm, found that Gov. Ed Rendell led Republican Lynn Swann, 49 percent to 36 percent, while Democratic challenger Bob Casey was ahead of Sen. Rick Santorum, R-Pa., 50 percent to 40 percent.

In both cases, the numbers were essentially unchanged from the firm's last poll in June, with slight shifts, within the survey's 3 percent margin of error, in favor of the Democrats.

The survey conducted from July 14 through July 18 was the first public poll released since Mr. Santorum's campaign began an emphasis on the immigration issue as an argument against his rival. Mr. Santorum voted against a Senate bill that would have allowed a path to citizenship for some illegal immigrants, while at the same time toughening penalties and border security against illegal immigration. Mr. Casey, the state treasurer, said he would have voted for the bill.

The survey found Pennsylvanians unsympathetic to illegal immigration. Overwhelming majorities supported the construction of a wall along the nation's southern border, and opposed amnesty for illegal immigrants working in the United States. Yet by the middle of the month, after the Santorum campaign began airing ads highlighting the issue, it had yet to translate into any measurable traction for the incumbent.

The data offered no clues as to whether that lack of movement was traceable to a public tuned out to politics in mid-summer, to the fact that voters were distracted by the upsurges of violence in the Mideast, or whether immigration was just not as high a political priority for Pennsylvania voters as for those in some other states.

Mr. Rendell's overall position four months before the election was considerably better than Mr. Santorum's. His job approval numbers, however, were only slightly better. Forty-six percent said they approved of Mr. Santorum's performance and 47 percent of Mr. Rendell's; 46 percent disapproved of the senator and 39 percent disapproved of the governor.

But Mr. Swann, the former Steelers wide receiver, continued to slip as his unfavorable numbers nearly equaled those of the incumbent. Earlier in the race, in a variety of published polls, a higher percentage of voters were undecided in their overall opinions of Mr. Swann, while the proportion with an unfavorable opinion was significantly lower.

The Republican candidates certainly weren't helped by the voters' views of President Bush. Only 26 percent of those surveyed said they approved of the president's overall job performance. In a state that the president lost by relatively small margins in 2000 and 2004, and one that he visited more often than any other in his first term, that was strikingly low, significantly below his national numbers.

Nationally, according to a compilation by the Web site realclearpolitics.com, Mr. Bush's recent job approval ratings have averaged slightly more than 39 percent.