Sprague — Retired Norwich police Detective Mark Lounsbury will seek the Republican nomination to challenge three-term incumbent Democratic state Sen. Cathy Osten in the 19th Senate District this fall.

Lounsbury, 57, unsuccessfully challenged Osten for the first selectman seat in Sprague last fall. He said he was pleased to have made a competitive run — losing 515 to 392 — for the seat and has remained active in town, raising issues and questioning Osten’s leadership approach. He had to give up his seat on the Board of Finance to run for first selectman.

“It’s time that people had someone who cares about them and truly represents them in Hartford,” Lounsbury said in his news release announcing his candidacy. “Protecting the interests of and creating opportunities for people who are trying to make it through these financially difficult times through hard work, sacrifice and taking risks is a Senator's primary responsibility.”

Lounsbury said he filed paperwork to form his campaign committee on Tuesday and now is contacting Republican Town Committees in the 10-town Senate district that runs from Hebron and Marlborough to Norwich, Ledyard and part of Montville.

Lounsbury said he plans to apply for funding through the Connecticut Citizens’ Election Program. He needs to raise at least $15,000 in contributions ranging from $5 to $250 from at least 300 donors from 19th District towns to qualify for $35,000 in a primary race and $75,000 for the general election.

Osten plans to seek re-election and also has filed campaign committee documents.

Lounsbury was an officer with the Norwich Police Department from 1989 to 2011, retiring as a detective. He and his wife, Amy, live in Baltic.

c.bessette@theday.com