Kerwin completed his doctorate in political science from Johns Hopkins University in 1978 and continued to teach until 1989, when he became the dean of the school.

Kerwin put his understanding of policy implementation to use in executing segments of then-University president Benjamin Ladner's 15-Point Plan, including the establishment of a new faculty senate.

Following the American University Board of Trustees' decision to suspend Ladner on August 25, 2005, Kerwin was named Acting President.

Kerwin's academic work focuses on public policy, administrative and regulatory processes and implementation and American government.

In the Chronicle of Higher Education survey of college presidents' salaries for 2007–08, he was fifth in the nation with a compensation of $1.4 million as a result of his 20-year signing bonus.