Even though I'm not a huge fan of Robert Casey Jr., I would rather vote for him over the worst senator in U.S. history.
As much as I hate Santorum...John C. Calhoun? Jesse Helms? Strom Thurmond? Joe McCarthy?
Rick Santorum is one of the worst Senators who ever served and easily the worst one who served during my lifetime. You are definately right that Strom Thurmond, Jesse Helms, John Calhoun and Joe McCarthy were more reactionary than Rick Santorum though.
What makes him specifically stand out as "worst" (which I assume means right-wing or something close to that) as opposed to the rest of the Senate?
His extremely hardline neoconservative foreign policy views, his hate-filled positions on gay marriage and gay rights in general, his support for Earmarks, the No Child Left Behind Act, the Medicare Prescription Drug Act and his opposition to the libertarian elements in the Republican Party are just some of the reasons why I despise Rick Santorum, along with his controversial public comments and extreme partisan, confrontational style of politics.