Currently watching the series for the first time on DVD. Why oh why did he leave the show? I'm assuming it had something to do with money. Creator Aaron Sorkin and exec Thomas Schlamme also left the show at the end of season 4. Wtf????
Rumour was he felt underappreciated. The idea was that Martin Sheen was the star, and Rob felt that actually he was a bigger star than Martin Sheen (not in the show but in general) and should therefore have his name first and should get paid as much as Martin Sheen.
Just a rumour from back then mind you...
Doesn't quite go that way. OP, check West Wing's message board and a thread called 'Rob Lowe's Departure' there is more info there.
~Krys~
My mother has me tested. I AM Kraz!:D
He discusses this in his book, Stories I Only Tell My Friends. I'm listening to it on CD and he hasn't quite finished The West Wing period at this point of my listening. But his agent negotiated an agreement that Rob would take half his normal salary upfront to fit the show's budget constraints, but he would get top billing. Originally, Sheen was supposed to appear in just a few Season 1 episodes, but the network wanted more of him, so his agent was able to negotiate a bigger paycheck. A few years in, the "lesser known" actors, such as Janney, Whitford, and Spencer, banded together to demand a raise, but they left Rob out of their negotiations. Rob's agent apparently didn't then have the leverage to get a raise for Rob, who (as I mentioned upfront) was taking far less money than he could have gotten elsewhere as a favor to Sorkin to get the show done.
Sorkin originally wanted "no names" in the cast, but the network wanted someone with known drawing power, and Lowe filled that role initially. Obviously, all the other actors got to be pretty well-known, too, over time.