Republican Mezzancello squeaked by Democrat José Berra in a special election for the vacated seat left by Michael Schiliro when Schiliro became town supervisor.
Mezzancello won the November election by 22 votes, and only when absentee and affidavit ballots were counted 10 days after the election.
The seat will again be up for election in November, when Schiliro's original term was to have ended.
Mezzancello is currently a member of the North Castle Planning Board.
The swearing-in ceremony will take place at 7 p.m. at Town Hall, 15 Bedford Road. All are welcome.
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