The director of free-market think tank the Institute of Public Affairs has confirmed he is considering running for preselection in Ted Baillieu's prized seat of Hawthorn.

The Napthine government was caught off guard on Friday when former premier Ted Baillieu announced he was quitting politics to make way for a "fresh face", leaving the Liberal Party clambering to find a new candidate less than 100 days from the state election.

IPA director John Roskam and Denis Napthine's legal counsel John Pesutto have firmed up as the frontrunners.

Mr Roskam, who has worked for the Kennett and Howard governments and also Rio Tinto, told The Age on Sunday that he was seriously thinking about running for preselection.

"I am very encouraged by the grassroots support I have received."