(CNN) - Republican challenger Pat Toomey leads Sen. Arlen Specter of Pennsylvania by 10 points in a possible November showdown, according to a new poll.
A Franklin and Marshall College survey released Wednesday morning indicates that 44 percent of likely voters back Toomey, with 34 percent supporting Specter and 16 percent undecided. But according to the poll, among all registered voters in Pennsylvania, Specter leads Toomey 33 percent to 29 percent, with nearly 3 in 10 undecided.
A Franklin and Marshall survey conducted last month indicated Toomey had a 14 point lead among likely voters and was deadlocked with Specter among registered voters.
Toomey is a former congressman and former head of the Club for Growth – a limited-government and anti-tax organization. Specter, a five-term senator, switched parties from Republican to Democrat last spring, saying at the time that the difficulty in winning the Republican primary against Toomey was a factor in his decision.
The poll also indicates that Toomey tops Rep. Joe Sestak 38 percent to 20 percent among likely voters in a hypothetical general election matchup, with nearly 4 in 10 undecided. Among all registered voters, Toomey slightly leads Sestak 25 percent to 22 percent with more than half undecided.
Sestak, a two-term congressman from southeastern Pennsylvania and former Navy admiral, is challenging Specter in May's Democratic primary. According to the poll, Specter leads Sestak 33 percent to 16 percent among likely Democratic primary voters, with nearly half of those questioned undecided.
The Franklin and Marshall College poll was conducted February 15-21, with 954 registered Pennsylvania voters questioned by telephone. The survey's sampling error for registered voters is plus or minus 3.2 percentage points.
Follow Paul Steinhauser on Twitter: @psteinhausercnn