Duncan says he won't make a bid to succeed Premier Dalton McGuinty and won't run for re-election.
But he says he will support his friend, former cabinet minister Sandra Pupatello, if she decides to throw her hat in the ring.
Duncan says most of the legwork on the next budget will be done by Jan. 27, then he'll hand off the more contentious decisions to the next finance minister, who could deliver a budget at the end of March.
McGuinty made a surprise announcement last week that he was stepping down after 16 years as Liberal leader and nine as premier.
Several other potential leadership candidates are said to be considering a bid, such as Municipal Affairs Minister Kathleen Wynne and former MP Gerrard Kennedy, who lost to McGuinty in 1996 by just 140 votes.
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