You ready for the biggest piece of TV casting all season?

Former West Winger Rob Lowe is joining the cast of ABC's sublime family drama Brothers & Sisters as a love interest for Calista Flockhart. And get this: He's playing another politician - a Republican senator who Flockhart's Kitty meets when he appears as a guest on her show, "Red, White & Blue."

Brothers & Sisters cocreator Jon Robin Baitz tells me the part was "tailor-made" for Lowe. "It's funny and smart and charming. It had to happen."

Lowe's first day on the set is Friday, and he debuts on Nov. 19.

Told y'all it was big!