A new voter survey finds Rick Santorum has a six-point lead over Mitt Romney among likely Republican voters in Pennsylvania -- 41 to 35 percent.

The Quinnipiac University poll is the third in a week to show a neck-and-neck race leading up to the April 24 primary.

The latest survey is more finely tuned than previous polls -- it includes only those Pennsylvania Republicans who say they're likely to vote.

Tim Malloy, a Quinnipiac spokesman, says despite the former Pennsylvania U.S. senator's slim lead over Romney, 57 percent of those surveyed say Santorum should stay in the race, because he's helping the GOP.

"Maybe they aren't completely committed to Mitt Romney and they want to hear more," Malloy said. "But Pennsylvanians we polled seem to believe that Rick Santorum should stay there. He says he's staying all the way."

The results bear out findings of other recent polls -- that Santorum's lead in his home state is shrinking from the double-digit command he had here a month ago.

A Mercyhurst College poll shows Santorum leading Romney by six points. Last week, a Franklin and Marshall College poll found Santorum's lead to be just two points, down from nearly 30 points a month before.

Over the weekend, Santorum criticized the pollsters behind that report, saying he expects to do exceptionally well in Pennsylvania.

The Quinnipiac survey has a margin for error of 3.9 percent.