He is not a perfect candidate, but once again proved that he can, in the face of daunting expectations, deliver a simply breathtaking speech at an absolutely pivotal moment. Masterful performance to match a brilliantly written speech. Conversational at times, lofty at others - and studiously serious throughout, in an apparent attempt to demonstrate that he possesses the demeanor of a plausible president. Superhumanly poised, he exhibited no jitters, never rushed, and married his own cadence to the rhythms of the audience's reaction.
Hitting Bush and McCain like a pro, he damned with faint praise, mocked with humor, and emphasized issues on which the Republicans are vulnerable.
In the process, Obama appeared to achieve every goal the pundits and political backseat drivers had set out for him in advance: he showed his heart, emphasized the economy, and, most of all, looked like a president. Worlds better than the revelatory 2004 convention speech that set him on the course to the nomination.
— by Mark Halperin