“It is difficult to cast a negative vote on someone with the qualifications and background of Dean Kagan, but we have a major problem of institutional standing to find out from a nominee what the nominee thinks on important questions,” Specter said, referring to her title as dean of Harvard Law School.

“I have gone to some length to try to find out more about Dean Kagan. In the absence of being able to do so and to have a judgment on her qualifications, I am constrained to vote no,” he said.

Seven Republicans voted for Kagan, including Sens. Jon Kyl (Ariz.), Tom CoburnTom Coburn'Path of least resistance' problematic for Congress Freedom Caucus saved Paul Ryan's job: GOP has promises to keep Don't be fooled: Carper and Norton don't fight for DC MORE (Okla.) and Orrin HatchOrrin HatchChaffetz calls for ,500 legislator housing stipend Industry 'surprised' by DOJ appeal in data warrant case US, South Korea can bury the trade barrier hatchet this week MORE (Utah).
Specter was also a Republican member of the Senate Judiciary Committee, which declined to take up Kagan's nomination to the U.S. Court of Appeals for the D.C. Circuit in the late nineties. Former President Bill ClintonBill ClintonJared Kushner hires Abbe Lowell for legal team Overnight Energy: Trump White House kicks off 'Energy Week' Bill Clinton: 'The water is going to keep rising’ whether US stays in Paris or not MORE nominated her to the bench in 1999.  

Recent polls show Sestak has pulled ahead of Specter in the primary race.
 
A new Muhlenberg College poll gives Sestak a four-point lead, 46 percent to 42 percent. A new Rasmussen poll shows Sestak ahead of Specter, 47 percent to 42 percent.
 
Sestak has gained political traction by raising Specter’s ties to prominent Republicans such as former President George W. Bush and former Alaska Gov. Sarah Palin.
 
Sestak launched an ad earlier this month with footage of Bush praising Specter as “a firm ally” he could “count on.”