The article does say, "Madrigal works as a union organizer for health care workers in King and Tulare counties." He quite obviously must be a Republican.
Even so, it's incredibly irresponsible of the journalist not to mention his reactionary tendencies at every conceivable opportunity.
OK, seriously, I'm not doubting what you wrote about your impression from simply reading this article--it's entirely possible that Madrigal's officially third-party or independent. I looked, though, and you won't be surprised to find a Tony Madrigal of Santa Cruz as a member of the Voter Services Committee of the California Democratic Party.
http://www.youtube.com/watch?v=fAUtZbG2D50
Si se pue’de?
A community organizer, Tony Madrigal is SEIU and an organizer for prop 22.