IIRC, Santorum ran against Arlen in the prior election and Dubya supported Arlen for some damned reason, which is what pushed Santorum out of the Senate. Karma’s a butch.
Toomey ran against Specter in the primary in 2004. Bush and Santorum supported Specter. It didn't sit well with PA's conservatives. However, Santorum lost in the general against Casey (D).