Although his part is very limited Alda actually is pretty much exactly as he should be. He really is a hatchet man used by Trippe for Hughes, but he does it all in a traditional sort of politician smile. Alda has that smile and has the right dynamic between being that friend of everyone politician face along with a more sinsiter quality in his eyes for when he needs to do what he must. Alda is fine in showing that Brewster is putting on always a bit of act that allows him to be a senator.
Past just the whole idea of who Brewster is Alda does not do all that much in the part, since we don't really know much about Brewster other than that he is against Hughes and for Trippe. There is never a moment that he is anymore than a typical poor sort of politician. Alda is never bad in the role, and is exactly as he should. Is it anything that needed to be awarded, no, is it very memorable, no, but it is technically a decent performance nonetheless.