A poll released Thursday showed the Pennsylvania Senate race between former Rep. Pat Toomey (R) and Rep. Joe Sestak (D) is in a dead heat.

A Quinnipiac University survey became the third released in the last week showing the Democrat leading the Republican. Sestak narrowly leads Toomey 48-46 percent among likely voters. A Sept. 22 Quinnipiac poll shows Toomey leading Sestak by 7 points, 50-43 percent. 

Earlier this week, Democratic firm Public Policy Polling's survey showed Sestak just barely leading the race, 46-45 percent, but that poll was considered an outlier by many. Then on Wednesday, an independent Morning Call/Muhlenberg College survey showed the Democrat leading 44-41 percent with 15 percent undecided.

The polls together are a sign that that the race is tightening after Democrats spent the past several weeks focusing on the contest.

President Obama appeared at a rally in Philadelphia about ten days ago intended to unite the Democratic base that polls show is trailing Republicans in enthusiasm. 

The Quinnipiac poll shows that trend might be turning around in the Keystone State. Toomey is beating Sestak 88-8 percent among Republicans and 56-35 among independents, but Sestak has grown his Democratic support to 89-7 percent. 

“Pennsylvania is a blue state and Democrats there have begun to come home,” Quinnipiac University Polling Institute assistant director Peter A. Brown said. “They are more engaged than they were earlier in the race."

Before the Quinnipiac poll was released, White House senior adviser David Axelrod said Tuesday that the "momentum has shifted" in the race, arguing it could serve as a bellwether of Democrats' chances of keeping their majorities in Election Day. 

“The polls are all over the place, with most of them showing a good sized lead for Pat Toomey," Toomey spokeswoman Nachama Soloveichik said in an e-mail Tuesday. "But the bottom line for Pennsylvania voters is a clear choice between more of the same reckless Washington spending and high unemployment with Joe Sestak, or a change in direction toward fiscal discipline and job growth with Pat Toomey."