First, never before in his life had he ever faced a first-rate Republican debating opponent. His races for the Illinois state senate and the U.S. House were one-party affairs. In his 2004 Senate race, the GOP candidate was Alan Keyes, who was brilliant but erratic and eccentric. In 2008, he ran against John McCain, a great American war hero, but not a great debater. The face-off with Romney was the first time that he had ever shared a stage with a Republican who spoke so crisply and knew his brief so well.
Second, he’s the incumbent. Like any president, he’s surrounded by people whose attitude toward him ranges from respectful deference to reverential awe. Everyone stands when he enters the room, and most people watch their tongues when they talk to him. Under those conditions, it is something of a shock for him to confront someone who talks back on equal terms.
Four years ago, President Bush’s face betrayed his annoyance when he had to listen to John Kerry. When Romney was speaking, we saw the same look on President Obama.