Poll: Dem senators lead in Florida, Ohio, Pennsylvania

Sens. Bill Nelson (D-Fla.), Sherrod Brown (D-Ohio) and Bob Casey Jr. (D-Pa.) all hold comfortable leads over their Republican opponents, according to a new survey from Quinnipiac University, The New York Times and CBS News.

All three are favored for reelection in their swing states, but Nelson and Brown in particular have been targeted by Republicans for possible defeat in the fall, and have already faced a slew of negative ads against them from GOP outside groups.

Nelson leads Rep. Connie Mack (R-Fla.) by 47 to 40 percent in Florida, Brown leads Ohio state Treasurer Josh Mandel (R) by 51 to 39 percent and Casey leads businessman Tom Smith (R) by 55 to 37 percent. All three have wider leads over their opponents than President Obama has over Mitt Romney in the states.

The Hill rates Florida and Ohio as "lean Democratic" and Pennsylvania as "likely Democratic" in its race ratings.

The polls, conducted from July 24-30, had large sample sizes of more than 1,000 voters apiece and margins of error of plus or minus 2.9 percent in Florida and Pennsylvania and 2.8 percent in Ohio.

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