Fresh off his victory in Pennsylvania's GOP gubernatorial primary, commonwealth Attorney General Tom Corbett raised some eyebrows by conducting a probe into his opponents on Twitter.

Corbett used grand jury subpoenas in an attempt to unveil the identities of his harshest critics on the microblogging site.

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Earlier this month, Corbett's office subpoenaed the online social networking site Twitter Inc., seeking identifying data on "CasablancaPA" and "bfbarbie." Both daily excoriate Corbett and his office's long-running political-corruption investigation known as Bonusgate.

The subpoena was apparently part of prosecutors' efforts to show one Bonusgate defendant's lack of remorse as he awaits sentencing.

But news of the subpoena unleashed a cascade of criticism from First Amendment and electronic-privacy advocates, who contend that Corbett is engaging in a Big Brotherlike attempt to silence and intimidate people who don't agree with him.

Twitter, based in San Francisco, has declined to turn over the information. The ACLU of Pennsylvania says it will seek to quash the subpoena on behalf of the two anonymous tweeters.

The issue promptly entered the governor's race, with Corbett's Democratic opponent, Dan Onorato - fresh from his own primary victory - saying in Philadelphia that he found it "outrageous" and "unbelievable" that the attorney general would use the powers of his office to subpoena critics.

— Cross-posted from the Twitter Room.