In the first of what is expected to be several major personnel changes, Governor Deval Patrick’s chief of staff, William “Mo” Cowan, is leaving the administration and will be replaced by the director of communications, Brendan Ryan.

In appointing Ryan, Patrick is turning to a 31-year old aide who has been the longest member of the governor’s senior staff and inner political circle. He first joined up with Patrick in 2005 at the outset of his gubernatorial campaign, travelling every day with the candidate in what began as a longshot battle for the Democratic nomination and turned into a landslide victory in November 2006.