What was Kavanagh's job in Lincoln's household in Abe Lincoln in Illinois?

Kavanagh is a secret service agent who moves in to protect Lincoln immediately after he is elected president. His presence indicates the way that the office distances the man from the men who helped him get there. Immediately after the election returns are announced, Kavanagh moves in, coming between Lincoln and the people, walking before Lincoln through doorways to look for assassins. His concern is not just a matter of paranoia; as he points out, there were many threats on Lincoln's life by Southerners who felt that he would endanger their right to own slaves. Audiences, of course, know that Lincoln was killed by an assassin, so all of Kavanagh' s precautions have an element of prophecy to them.