(CNN) – A new poll indicates it's dead even in the battle for Pennsylvania's open Senate seat.
According to a Quinnipiac University survey released Wednesday, 43 percent of Pennsylvania voters back Rep. Joe Sestak, the Democratic nominee, with an equal number supporting former Rep. Joe Toomey, the Republican nominee, and 12 percent unsure.
Toomey held a 42 to 40 percent advantage in Quinnipiac's last poll, which was conducted in May.
Sestak, a former Navy admiral and current two-term congressman from southeast Pennsylvania, beat incumbent Sen. Arlen Specter in May's Democratic primary. Specter, a five-term senator, switched parties from Republican to Democrat in the spring of last year. At the time of the party switch, he cited the difficulty in winning the Republican primary against Toomey as a factor. Besides his service in Congress, Toomey is also the former head of the Club for Growth, a limited-government and anti-tax organization.
According to the poll, Democrats back Sestak 77 to 11 percent, with Republicans supporting Toomey 82 to 11 percent and Independents backing Toomey 44 to 35 percent. Toomey's advantage among Independents is down 7 points from the May survey.
The poll indicates that 35 percent have a favorable view of Toomey, with 13 percent seeing him unfavorably, and just over half saying they don't know enough about him to form an opinion. Sestak holds a 31 percent favorable rating, with one in five seeing him in an unfavorable light, and nearly half saying they don't know enough about him to form an opinion.
"Congressman Joe Sestak, a decided underdog who knocked off U.S. Arlen Specter in the Democratic primary, has now closed an 8-point gap in the last three months to tie Pat Toomey," says Peter Brown, assistant director of the Quinnipiac University Polling Institute. "But the Senate race remains wide open, since at this point about half of the voters don't know enough about either candidate to form an opinion."
The poll's release comes one day after the Toomey campaign announced it brought in $1 million more than the Sestak campaign in fundraising over the past three months.
According to the poll, by a 48 to 42 percent margin, Pennsylvania voters say that President Barack Obama doesn't deserve re-election in 2012. And 41 percent they would vote for an unnamed GOP candidate, with four in ten saying they would vote for Obama.
The Quinnipiac University poll was conducted July 6-11, with 1,367 Pennsylvania voters questioned by telephone. The survey's overall sampling error is plus or minus 2.7 percentage points.
–CNN's Charles Riley contributed to this report
–Follow Paul Steinhauser on Twitter: @psteinhausercnn