Paul is a professor of Politics. He has twice been the convenor of Politics and International Relations in 2007-08 and 2012-16. He has also been deputy head of the School of Social Sciences between 2018 and 2021.

Paul specialises in Australian political history with a particular focus on biography, political leadership and political parties. He is an author and editor of twelve books. These include his acclaimed biography, Keeper of the Faith: A Biography of Jim Cairns (2002); Neither Power Nor Glory: 100 Years of Political Labor in Victoria (2012); and (with Paul 't Hart and James Walter); Settling the Office: The Australian Prime Ministership from Federation to Reconstruction (2016); and The Pivot of Power: Australian Prime Ministers and Political Leadership, 1949-2016 (2017).

Paul is a two-time recipient (in 2013 and 2019) of the Henry Mayer Book Prize for Australian Politics (awarded biennially by the Australian Political Studies Association for the best book on Australian Politics).

Paul has been a prolific commentator on Australian politics in the print and electronic media, including contributing more than fifty op/ed pieces to the Melbourne Age and for a number of years has had a regular politics segment on the Evening Program on ABC Radio Melbourne.

In 2018, Paul was appointed Visiting Cabinet Historian to the National Archives of Australia.