North Stonington — Longtime Republican incumbent Nicholas H. Mullane said Monday that he will not seek another term as first selectman this fall.

Mullane said he instead will run for a seat on the three-member Board of Selectmen, with Shawn Murphy, a Republican with experience on the boards of finance, education and selectmen, running for first selectman. Mullane has been first selectman almost continuously since 1983 and is in his 15th term. He also served as a selectman from 1995 to 1997.

"I'm honored to run with Shawn," Mullane said. "I've been looking for a way to step down ... and this is a very qualified candidate."

With Mullane in charge, town meetings have been run informally, with residents allowed to speak on issues during the meeting, not just in a public comment period.

Mullane was challenged by Robert L. Testa in 2007, 2011 and 2013. Testa received the Republican nomination over Mullane in 2011, but Mullane prevailed in a primary. With Mullane as first selectman and Testa holding a seat on the board, meetings have sometimes been contentious.

With Foxwoods Resort Casino as a neighbor, and the Eastern Pequots' reservation in North Stonington, Mullane has been outspoken on tribal sovereignty issues. He recently traveled to Washington to testify against changes to the federal tribal recognition process.

Murphy, who was Mullane's running mate in the 2007, 2009 and 2011 elections, first served on the Board of Finance in 2001, eventually becoming its chairman.

From there he moved to the Board of Education, where he spent time on the board's personnel, facilities and finance committees.

Murphy, who did not run for public office in 2013, said on Monday that his "semi-retirement" has freed up the time he needs to return to public service.

Murphy directed auxiliary services at Connecticut College until recently but said he's now "interested in continuing to serve the town and doing so on a full-time basis."

Murphy cited his experience with all three boards as well as his work with administration and finance in past jobs as advantages he has over other potential candidates.

If elected, he said, his first move would be to ask board and commission chairmen what their concerns are.

Murphy has registered as a candidate and plans to seek the Republican Town Committee's endorsement during its July 28 caucus, which begins at 7:30 p.m. at the North Stonington Senior Center.

l.boyle@theday.com