Democratic Illinois Sen. Barack Obama led Republican Arizona Sen. John McCain in three battleground states, including Pennsylvania, in new presidential election surveys released yesterday by Quinnipiac University.

The results showed Mr. Obama ahead in competitive races in Florida and Ohio, where his margins were 47 percent to 43 percent and 48 percent to 42 percent, respectively.

The Democrat held a more substantial advantage, 52 percent to 40 percent, in Pennsylvania -- a state in which he was trounced by New York Sen. Hillary Rodham Clinton in the party's primary in late April.

Mrs. Clinton won all three states during the primary season, although neither candidate had campaigned in Florida.

Together, the results could be seen as a rebuttal to the Clinton campaign's frequent argument that Mr. Obama's losses among Democratic voters in swing-state primaries spelled general-election vulnerability for the Illinois senator.

"Finally, getting Sen. Hillary Clinton out of the race has been a big boost for Sen. Barack Obama," Peter A. Brown, assistant director of the university's polling institute, said in a statement released with the new results.

Quinnipiac has polled all three states regularly this year. This was the first time that Mr. Obama had led over Mr. McCain in all of them.

Another polling organization, American Research Group, or ARG, released a new Florida survey yesterday with similar results. The Democrat's Florida margin in the ARG survey was 49 percent to the Republican's 44 percent.

Another ARG survey released yesterday showed Mr. McCain trailing in New Hampshire, one of the states that went Democratic in 2004, but that Republicans have discussed as a target this year.

In all three of the new Quinnipiac polls, the majorities cited the economy as the most important issue in the campaign. By even bigger margins, the respondents agreed with Mr. Obama's view that the decision to go to war in Iraq was a mistake.

Surveyed registered voters were closely divided about the two candidates' positions regarding the war's future and whether troop withdrawals should follow a fixed timetable or, as Mr. McCain contends, the pace of withdrawal should be dictated by progress toward a more stable and secure environment.

In all three states, Democratic majorities supported the choice of Mrs. Clinton as the Democratic vice presidential nominee. But the Quinnipiac analysts noted that, in each case, strong pluralities of independent voters -- the variable for the fall campaign -- opposed the suggestion that the New York senator should serve as Mr. Obama's running mate.

In Pennsylvania, as in Ohio and Florida, Mr. Obama's advantage was strongest among women, blacks and younger voters. The Democrat also had slim leads among the state's white voters and older voters, but Mr. McCain edged him among men.

In the Pennsylvania results, Mr. Obama carried women, 57 percent to 34 percent, but men favored Mr. McCain, 47 percent to 45 percent. Whites broke narrowly in Mr. Obama's favor, 47 percent to 44 percent, while black voters were just short of unanimous in his favor, 95 percent to 1 percent.

Mr. Obama was ahead in almost every region of the state, but, as in the primary, he did substantially better in the east -- particularly in the city of Philadelphia, where his margin was an overwhelming 77 percent to 18 percent. Elsewhere in the southeast, he led, 54 percent to 39 percent.

The Democrat led in Allegheny County by 51 percent to 40 percent, but barely edged his GOP rival in the balance of southwestern Pennsylvania, 46 percent to 44 percent.

In the state's traditionally Republican center, the two candidates tied, with 44 percent each.