looks like theres a new sheriff in town

Looks like theres a new sheriff in town is an expression which has become a cliche because of how often it is used. This phrase means that there is a new authority figure taking charge of a group or organization, whether formal or informal. A sheriff in town is usually the person who is in charge of the way the town runs, therefore when used figuratively, this idiom means that there is a new leader or authority figure.