Because Stephen Harper was a self-described “radical right-wing ideologue”, he was the only one who could make the conservatives more Liberal.
Because Barack Obama was so anti-war, he was the only one who could make the Democrats more pro-war than Republicans.
In both cases it was each man’s close association to a particular cause that gave him the credibility and therefore the power to fundamentally change it.
And it is because Justin Trudeau is perhaps the most identifiable Liberal that he, and he alone can make the party more conservative, and, as they aren’t mutually exclusive, more progressive. Trudeau has