"Randall Morck, visiting professor of Canadian studies at Harvard, said Ignatieff will be “a breath of fresh air” to the Liberal Party, which has a solid shot of obtaining a majority in the next election. "
A majority? Fat chance. Where are the 52 Liberal seats going to come from? The West? Quebec? The only remaining place that they can realistically pick up seats is Ontario, where even if they were to win every seat from the Tories, they would still fall a dozen short of a majority.
Which answers the question of why Manley, Tobin, and McKenna likely do not want to be the Liberal leader at this time. No prospects but opposition.