Congressman Thiele is a Democratic representative from Rhode Island. He is second-term congressman who in 2003 is the lone "nay" vote against the confirmation of Bob Russell as vice president.
Josh Lyman and Leo McGarry believe he is voting nay because he wants to raise his profile by making talk show appearances. Josh threatens him with President Bartlet's displeasure and political opposition, but Thiele genuinely believes Russell is a bad choice and stands firm. He calls out Josh for rolling over on Secretary Berryhill and settling for a party hack.
Josh plans to leak it that Thiele wanted to be vice president instead, which will make him look ridiculous considering he is a second-term congressman from the smallest state, but Ryan Pierce uses the fact that Thiele interned for his uncle Senator Pierce to leverage him into changing his vote. Josh has no idea why he did, but he doesn't leak his claim to the Post.