The city is holding a special election on Tuesday to take up a referendum on Mohegan Sun’s proposed casino at Suffolk Downs. Voting hours are 7 a.m. to 8 p.m. Mohegan Sun is seeking a state license to build a $1 billion resort casino development on 42 acres in Revere owned by Suffolk Downs. A previous proposal by Suffolk Downs and Caesars Entertainment for a casino in Revere and East Boston was rejected by East Boston voters last Nov. 5, the same day Revere voters endorsed it. Under a host agreement that was signed Dec. 23, Mohegan Sun would pay Revere $33 million up front, and minimum annual payments from $25 million to $30 million. Applicants for casino licenses must secure a host agreement and support from a local referendum.