The phrase "to become mayor" means to be elected or appointed as the chief executive officer of a city, town or other local governmental unit. Full definition
You immediately become mayor of your new town, and making its citizens happy is key. (primagames.com)
People close to both men privately acknowledge that there's bound to be more conflict coming between them after de Blasio becomes mayor. (politico.com)
Have you had to change your thinking since becoming mayor, away from that disruption mindset? (canadianbusiness.com)