Rex Murphy in the Globe & Mail: 

Even after two autobiographies, Mr. Obama remains something of a floating, uncrowded presence. His story (and he is so impressively self-aware as to have made the most acute comment on it) is temptingly open-ended, very much a page to be written on. He himself has written, most memorably: “I serve as a blank screen on which people of vastly different political stripes project their own views.”

That is as bold a statement as it is an insightful one. Bold, because it is a remarkable confession from a presidential hopeful. Insightful, because it matches the facts. There are not many personalities so fluid or vague on which an attempt to “project” a storyline would take hold. Imagine, for example, projecting a “rewrite” of Donald Rumsfeld. There’s too much of Mr. Rumsfeld already there to offer hospitality to new material.

Mr. Obama, however, has a kind of welcoming emptiness. Eager acolyte or stern observer, both find it difficult not to add, or project, the most flattering, even jubilant, fill-ins. The Obama candidacy, in its rocket-blast phase when he outsoared Hillary Clinton, drained the dictionaries of every superlative. The great “O” had them swooning in the stands. Why?

True, Oprah had passed her potent wand over him, but even the afternoon regent of a thousand therapies has stays on her sorcery. Mainly, his was very much a candidacy constructed by those who were drawn to him. If there was any meaning to that fortune-cookie poeticism that “we are the ones we have been waiting for,” it was that his campaign was a feedback loop. People saw what they came to see. Mr. Obama was the slate; the crowds brought their own chalk.

This is the nature of Mr. Obama’s particular kind of charisma. People project their best wishes on him, they fill in the blank of a very attractive and plausible outline. His is not, emphatically, a charisma of deeds. For what has he done, save run for president? He is an accommodating vessel – cool, smart, biracial and “unfinished.” This is the Gatsby quality of him that others have noted. Like Gatsby, he is a receptacle of others’ glamorous invention.