state legislaters
That would be the Congressmen-At-Large.
Senators are the members of the House that are chosen for a state's entire population. Representatives are chosen to represent a portion of their state.
In states with a low population, members of the House of Representatives are chosen in the districts. This is to create a balance in the legislative representation.
The prime minister of Australia is chosen by a majority of the members of the house of representative's. The members of the house of representatives get there by being voted for by the general population.
At-large.
There are two Senators for every state regardless of size. House members are chosen according to the population in every state.
because they were all chosen by the president
They are chosen by the leaders of the house and senate.
The speaker of the house gets chosen by a vote of the members of the house. The constitution does NOT require that the speaker be an elected member of congress.
Population
The House of Representatives is closer to the people because the members are chosen to reflect the true populace. The House has members proportional to the state's population while the Senate has only two seats per state, regardless of the state's population.
The House of Representatives are chosen based on a state's population. The number of representatives each state has is subject to change.
population