President Obama has announced his fourth Chief of Staff since taking office back in 2009. Denis McDonough, who is one of the President’s trusted and closest advisers, will be taking the position of Chief of Staff after noon today. McDonough is currently the deputy national security adviser and has been since 2010 but will be stepping down from that position to take his new one. The working relationship that McDonough has with President Obama goes back to Obama’s days as a Senator. Read more below. Julie A.