The secret scope grievance "settlement" and Armando's resolution that passed so overwhelmingly during the subsequent backlash made him very popular. He received the most votes of any candidate, FO or Capt, by a good margin.
If he wants to be the first FO ever elected Chairman, I think he could do it. I doubt if he will try though. He is an unassuming fellow and wouldn't want to be seen as "overstepping".