The Liberal leadership race lost a contender Wednesday, as former infrastructure minister John Godfrey dropped out because of poor health.
He said doctors have not yet confirmed what is wrong with him, but he has been ill for about two months.
"I have just not been feeling great, and I want to be in good physical shape," he told reporters in Ottawa, saying he made his decision after receiving inconclusive test results Monday evening.
"The irony is the campaign was gathering strength from all points of view."
Godfrey, 63, had said he wanted to draw attention to issues such as environmental sustainability, child care and social justice during the Liberal race.
He said he would continue to push on those issues as an MP and the critic for intergovernmental affairs.
Godfrey was a university professor, an economist and the editor of the Financial Post newspaper before entering politics in 1993.
The member of Parliament for the Toronto riding of Don Valley West was the second person to declare he would run to replace former prime minister Paul Martin at the helm of the Liberal Party of Canada.
The first was Toronto-area lawyer Martha Hall Findlay.
Since then, MP Michael Ignatieff and former environment minister StÃ©phane Dion have entered the competition.
As well, Gerard Kennedy left his post as Ontario's education minister last week to free up time to organize his federal leadership bid.
Former Ontario premier Bob Rae is also expected to announce his candidacy.