Greg Stanton has announced his last day as Phoenix’s mayor will be May 29. He’ll leave to focus full-time on his congressional race. The move will trigger a big shake-up inside city hall after he leaves.

MORE: Mayor Stanton's Interview On The Show, May 11

Vice Mayor Thelda Williams will become the temporary mayor. Within 15 days, the City Council must choose either Williams or another member to serve as mayor until a special election is held.

Two current council members — Daniel Valenzuela and Kate Gallego — are already running for mayor. They’ll have to resign their council seats by August 8. It will then be up to the remaining six council members to appoint interim replacements until a special election takes place.