After returning to Edmonton, he ran for mayor in the 1913 election, in which he defeated incumbent William Short, receiving 50.2% of the vote in the two person race.

In office, he formed an alliance with future mayor Joseph Clarke (then an alderman) against those who wanted to drive prostitution and gambling out of the city.

His alliance with Clarke ended when the two came to blows in a meeting of Edmonton City Council.

Later in his term, he was convicted by Justice William Ives of voting on a matter in which he had a pecuniary interest and was, along with alderman James East, expelled from office on October 27, 1914.

[1] McNamara died on January 1, 1947, at 3:55 pm in Phoenix, Arizona, of heart failure.