Why does ward boss kelly send a boy to greet new arrivals in the harbor?

Ward boss Kelly sends a boy to the harbor to greet new arrivals to ask them if they need a job or a place to stay. He tells them that the people there hate the Irish. The boy also mentions that they can't get a job unless they meet the biggest ward boss in Boston. The ward boss is going to give a job and lodgings to the new arrival, register him as a citizen and a voter. Of course this will mean that the new arrival will have to vote for the Kelly's men in all the elections.

  the domino theory states that  if one country in a region came under the influence of communism, then the surrounding countries would follow in a  domino  effect.