(CNN) - A new series of Quinnipiac polls out of Ohio, Florida, and Pennsylvania appear to bolster Hillary Clinton's argument that she is better positioned than Barack Obama to beat John McCain in the crucial swing states.
According to the polls released Thursday, Hillary Clinton would beat John McCain in all three states by wide margins while Barack Obama would lose to the Arizona senator in Ohio and Florida and narrowly beat McCain in Pennsylvania.
CNN Polling Director Keating Holland said the poll could be a "early-warning sign" for Democrats, though cautioned early polls often are not predictive.
Specifically, the poll found Clinton tops McCain in Florida by 7 points (48 percent to 41 percent), in Ohio by 7 points (48 percent to 41 percent) and in Pennsylvania by 13 percent (50 percent to 37 percent).
Meanwhile the poll finds McCain would beat Obama by 4 points in Florida (45-41 percent) and by 4 points in Ohio (44 percent to 40 percent). Obama beats McCain in Pennsylvania, but by a narrower margin than Clinton does - he beats McCain by 6 points there, 46 percent to 40 percent.
According to Quinnipiac, the difference between Clinton and Obama's performances in the state can be traced to the fact that several Clinton supporters and white working class voters there say they will support McCain over Obama if the Illinois senator is the party's nominee. (Related: Can Obama win over the working class)
"This could be an early-warning sign for the Democrats, particularly since Obama did not do well in the Pennsylvania and Ohio primaries," Holland said. "On the other hand, any poll conducted in May - particularly when the primaries have not finished - may have little predictive value."
The last presidential candidate to win the White House without winning two of the three largest swing states was John F. Kennedy in 1960. (Kennedy won Pennsylvania that year, but lost Ohio and Florida.)
But the 2008 electoral map could look different than most recent elections, both the McCain and Obama campaigns have said. Each candidate has shown to strongly appeal to independent and moderate voters - meaning more states could be up for grabs this year than has been the case in past elections.
View more polling information at the CNN Election Center