Ambassadors represent the US government, or their country of origin, in place of the president or leader.
Legislators are members of the legislative branch of government, which is responsible for making new laws and changing existing laws.
A mayor is someone who is the highest ranking municipal officer in a city or town.
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A senator is someone who is elected in the central legislative body of a state (usually it concerns the upper, more prominent chamber of Parliament), by voters of a region or other territorial district, and fulfills this governing mandate for a number of years, according to the law.