According to the good folks at Think Progress, on March 1st Santorum attacked Senator Byrd for making a Hitler reference:
Byrd roused the ire of many Republicans when he tangentially referred to Adolf Hitler during a speech on March 1 defending cloture and the right to debate.
Sen. Rick Santorum, R-Pa., asked Byrd to retract his comments, stating they “lessen the credibility of the senator and the decorum of the Senate.” The Anti-Defamation League also criticized Byrd.
Hypocrisy, thy name is Republican.
And Crooks and Liars has the video of Santorum.