In November 2010, Portland voters approved a citywide referendum changing the city charter to recreate an elected mayor position that had previously been removed in 1923. From 1923 until 2011, city councilors chose one of themselves each year to serve as mayor, a primarily ceremonial position. On November 8, 2011, former State Senator and candidate for U.S. Congress Michael F. Brennan was elected. On December 5, 2011, he was sworn in as the first citizen-elected mayor in 88 years.
The new citizen-elected mayor serves full-time in the position for a four-year term, exercises the powers and duties enumerated in Article II Section 5 of the Portland City Charter, be elected using instant-runoff voting, and, like the rest of municipal government in Portland, be officially non-partisan.
The declared candidates filed paperwork with city hall to allow them to raise funds for their campaigns. The nomination papers became available on July 1 and the candidates were required to submit at least 300 valid signatures of Portland voters between August 15 and August 29 to be placed on the November ballot. As of the August 29 deadline, 16 candidates submitted their nomination petitions, and 15 petitions were validated: Bragdon, Brennan, Bryant, Carmona, Dodge, Duson, Eder, Haadoow, Lapchick, Marshall, Mavodones, Miller, Rathband, Strimling, and Vail. Bennett fell five signatures short of the required 300.
As of July 4, Christopher Vail was invalidated by city attorney Gary Wood from running due to his employment by the city as a firefighter but this was overturned shortly thereafter. As of July 8, Zouhair Bouzrara was in court facing charges after allegedly drinking alcohol, a violation of parole given to him a year early after being accused of threatening to kill a co-worker in July 2010. Bouzrara withdrew during the petitioning process.
On September 27, David Marshall was endorsed by the Maine League of Young Voters. On October 11, Portland Tomorrow, a group made up of some former charter commissioners and other supporters of the elected mayor referendum, endorsed Michael Brennan. On the same day, the Portland Education Association endorsed Nick Mavodones. On October 17, the Portland Press Herald endorsed Michael Brennan. On October 26, Jed Rathband received the sole endorsement from the Portland Regional Chamber of Commerce Political Action Committee. On November 1, Ethan Strimling received the endorsement of John Eder. On November 1, David Marshall received the endorsement of Maine Green Independent Party. On November 1, Nicholas Mavodones received the endorsements of Carpenters Local 1996 and AFSCME Local 481. On November 5, The Portland Daily Sun endorsed Michael Brennan.
Erick Bennett, Parkside resident, Republican blogger and campaign media aide to Governor Paul LePage, submitted nomination papers with insufficient valid signatures, announced Write-in candidacy on August 30 pending request of petition recount with Portland City Clerk's office