Republican Tom Corbett, Pennsylvania's attorney general, has double-digit leads over the top Democratic candidates for governor -- all of whom are ranked behind "don't know" when voters are asked whom they favor in the party's primary, according to a Quinnipiac University poll conducted Feb. 22-28.

Corbett leads Allegheny County Executive Dan Onorato by 42 percent to 32 percent with 24 percent undecided. Corbett gets stronger support from fellow Republicans (77 percent) than Onorato does from Democrats (64 percent). Among independents, Corbett leads 40 percent to 23 percent with 33 percent undecided. Corbett's margin is somewhat smaller than in December, when he led by 45 percent to 30 percent.

Corbett leads Auditor General Jack Wagner, 42 percent to 30 percent, with 26 percent undecided. Corbett has the support of 76 percent of fellow Republicans to Wagner's 63 percent among Democrats. Corbett leads Wagner among independents 40 percent to 19 percent with 37 percent undecided. That result is similar to where they stood in December