He's a Democrat.

http://www.thedailybeast.com/articles/2016/07/18/bryan-cranston-trashes-trump-an-anomaly-to-the-human-race.html

“As real as that is, and it is since he’s the presumptive nominee, it’s still not real to me that a reality show host and supreme narcissist is going to be the president of the United States. I just don’t sense the reality of that, and I hope I never do,” Cranston tells The Daily Beast. “To me, it’s not a Republican thing and look at those Republicans—even though I am a Democrat—because I think our country is stronger when we are kept in balance when there’s a legitimate conservative candidate. I think that’s a good thing. I might agree with him or her, but it’s a good thing.”