Fleming's political career began as an Alderman for the Ward of St. David's 1886 to 1890. In 1892 Toronto municipal election, he was elected mayor of Toronto. He was defeated in 1894 and 1895 but was returned to office in the 1896 Toronto municipal election and again the next year.
Fleming's political career started with a term as an alderman for Ward of St. David's from 1886 to 1890. He became mayor of Toronto in 1892, but lost his position in 1894 and 1895. However, he was re-elected mayor in 1896 and the following year.