In 1967 Tanzler ran against incumbent mayor Lou Ritter for the Democratic nomination. He ran on a ticket of reform as a "white hat", a supporter of consolidation of the City of Jacksonville and Duval County governments. In those days, the Democratic primary was the real contest in Jacksonville. Tanzler defeated Ritter in the primary, then easily defeated Republican William Hembree in the general election. Two months later, on August 8, 1967, voters approved the Jacksonville Consolidation. This meant Tanzler had to stand again for mayor of the new government on September 26. However, no one else filed, thus he became the first mayor in Jacksonville history to be elected unopposed. When consolidation took effect on October 1, 1968, Tanzler became the last mayor of the old city government and the first mayor of a consolidated Jacksonville.