The Mayor of Michel Delving, also called the Mayor of the Shire, was the only elected official in the Shire. Mayors served a seven-year term, with elections being held at Midsummer. Aside from also being the First Shirriff and the Postmaster, the Mayor’s other duty was to preside at banquets on holidays.
At the time of the Lord of the Rings, the Mayor of the Shire was Will Whitfoot, described as “the fattest hobbit in the Westfarthing” (which most likely took some doing). He was also known by the name Flourdumpling after the roof of Michel Delving collapsed and buried him in chalk, making him look rather like, well, a floured dumpling.
In LotRO, Will Whitfoot is part of the Shire Prologue Epic quest chain. Upset about his treatment at the hands of brigands, Mundo Sackville-Baggins demanded compensation from the Mayor. Rather than pay the money, Whitfoot sends the player to inform Lobelia that not a penny will be forthcoming.
During the War of the Ring, the Mayorship was disbanded by Lotho Baggins, who instead took up the title of Chief Shirriff, or just Chief. Will Whitfoot went to Bag End to protest all the damage being done to the Shire by Lotho’s Ruffians, but was waylaid on the road and locked up in Michel Delving. After the Scouring of the Shire, Frodo took up the position of Deputy Mayor until Will recovered from his incarceration, and took it upon himself to reduce the duties and numbers of the Shirriffs back to their pre-war levels. After Frodo’s resignation from the position of Deputy Mayor, Will Whitfoot was elected for another seven-year term, which would prove to be his last. He resigned at the end of it, and Samwise Gamgee was elected Mayor the next seven times. Along with Thain Peregrin I and the Master of Buckland Meriadoc the Magnificent, Mayor Samwise was named a Counsellor of the North-Kingdom by King Elessar. There is no record of who the mayors were before Will Whitfoot or after Sam Gamgee, but it is noted that Tolman Cotton was appointed deputy mayor during one Samwise’s later visit to Gondor.