Voters on Tuesday will head to the polls for the annual town election, and for the primary in the special election for US senator. The elections are being held on the same day, but voters will receive separate ballots. The town election features two contested races. One is a six-way contest for three seats on the Board of Selectmen, and the other a four-way race for three seats on the School Committee. The special election is to fill the seat formerly held by John F. Kerry, who resigned from the Senate to become secretary of state. Polling hours are 7 a.m. to 8 p.m. for both elections.