The Obama on display in the second debate - and this week's third - was harder, chillier, sadder, and more somber. There was tension in the lines of his mouth. His speech was clipped, as if under continuous, rigorous control. His rhetoric did not soar - could not soar. The smile was rare and constrained.
But his command of detail and argument was rock-solid; his sentences, parsed. He spoke with a cold, disciplined energy. In repose (as seen in the split-screen reaction shots), he was often perfectly immobile, almost stony, as if posing for a portrait.
One word for all this would be presidential, in the sense of competent, seasoned, and sobered by reality. But that word also connotes the fearsome qualities of ruthlessness and brutality that any honest portrayal of the office of president of the United States must include in our day. Obama has inhabited the White House for four years; now the White House inhabits him.
Twice this autumn, Obama had performed before tens of millions of people - in his acceptance speech at the Democratic convention, and in the first debate - and each time, his performance was flat. At the convention, he seemingly hoped to summon the old Obama, to charm and soar. But that man was simply no longer available.
The truth appears to be that his muse deserted him sometime in the first year of his presidency. The result was a simulacrum of the old Obama, as if he were playing the part of himself.
Then, in the first debate, no such futile effort was even made, and there was no Obama at all, old or new. As so many commentators noted, in a sense he simply failed to show up. Perhaps he also thought that, well ahead in the polls, he did not have to bother to engage the pesky fellow who imagined replacing him in the White House.
At the second debate, the loss of the old Obama was apparently accepted, and a new one - existing, real, and working in the Oval Office - made his first appearance.
Has the presidency hardened Obama? Has it brutalized him? There are reasons for thinking that it has.
First, Obama has taken perhaps a heavier beating from his political opposition than most presidents.
The theme of Obama's life, expressed in his eloquent memoir Dreams From My Father and in the recent Frontline documentary The Choice, is reconciliation. His identity was not handed to him at birth. The son of a white mother and an absentee Kenyan father, raised in Indonesia and Hawaii, he was forced to figure out his place. He found it in the idea of reconciliation, both racial and ideological.
That was the theme of his defining convention speech in 2004, with its famous line: "There is not a liberal America and a conservative America; there is the United States of America." It was to be the theme of his presidency.
So, when an ideologically implacable Republican opposition threw the vision back in his face in his very first days in office, adopting a policy of scorched-earth opposition, the rejection was about more than policy; it affected his very being. The dreams from his father were at an end, and he was left, as he only slowly realized, with the themeless pragmatism that has become the hallmark of his administration.
Unable to find common ground with the Republican opposition, he cut deals with the other powers that immediately surround the presidency: the military and security apparatus, big pharmaceutical companies, banks, and the media. Perhaps more important was the permission he gave himself to commit violence and suppression: drone strikes that have killed children as well as terrorists, the futile "surge" in Afghanistan, the continued operation of the prison at Guantánamo Bay, the reliance on military tribunals, an unprecedented campaign against whistle-blowers, and the assertion of a right to order the assassination of foreigners and Americans alike at his sole discretion.
All this, too, stood behind the performance of the man on stage during the second and third debates. And if he is elected, it is this man who will govern.
The Obama of 2008 is not back. He is not coming back. He is gone forever.
Jonathan Schell is a fellow at the Nation Institute and a visiting fellow at Yale. This was distributed by Project Syndicate.