Senator
From Memory Alpha, the free Star Trek reference.
A senator is an elected person who sits in a Senate.
The Romulan Star Empire is one of the best known groups who utilize this style of government. Romulan senators are elected to the Romulan Senate. Romulan senators represent districts. (TNG: "Unification I")
At least three Senators represented the Romulan Star Empire on Deep Space 9 during the Dominion War - Letant, Kimara Cretak, and Vreenak. (DS9: "Tears of the Prophets", "Image in the Sand", "Shadows and Symbols", "Inter Arma Enim Silent Leges", "In the Pale Moonlight")
