Shirley Anne Warshaw, professor of political science at Gettysburg College, was quoted in a February 10 Bloomberg article regarding President Obama's Cabinet.
From Bloomberg:
“With 15 Cabinet-level departments as the government gets larger, it’s the White House that is at the center of the presidential orbit,” says Shirley Warshaw, a presidential scholar at Gettysburg College.
This trend has accelerated under Obama. There is a strong case to be made that presidential decision-making today would benefit from Cabinet members who have considerably more political and managerial experience than White House aides, who are predominately longtime Washington staff insiders.