CAPE ELIZABETH — Voting is under way in a special election for Maine House of Representatives District 121.

Democrat Kim Monaghan-Derrig and Republican Nancy Thompson are running for the seat that was vacated in May by Cynthia Dill. The Democrat left her House seat to run for an open state Senate seat, to which she was elected on May 10.

Both women are 52 and neither one has ever run for state office. House District 121 covers most of Cape Elizabeth, except for some northern portions that are part of District 123.

The polls will be open until 8 p.m. at the Cape Elizabeth High School cafeteria.

Thompson is an insurance agent and a 25-year resident of Cape Elizabeth with a record of community service. She is a well-known advocate for suicide prevention and education about mental illness. Her 18-year-old son, Timmy, the middle child of five, took his own life in July 2004.

Monaghan-Derrig, who grew up in Cape Elizabeth with six siblings, works in tourism marketing. She serves on the town’s school board, has a background in economic development and is pursuing a master’s degree in public policy at the Muskie School of Public Service in Portland.