One reason may be optics. Obama was scheduled to deliver the speech in a stadium seating 64,000 people. But on Wednesday, after Charlotte, N.C., had been pummeled by periodic rainstorms all week, organizers moved the event to the convention hall.
The last two stadium acceptance speeches, in 2008 and 1960, were delivered in Denver and Los Angeles, where it seldom rains in the summer. That's not true of Charlotte -- or of Tampa, Fla., where Republicans took a risk by scheduling their convention at the start of hurricane season.
So Obama spoke at the same podium as Bill Clinton had the night before. The comparison was not flattering to the 44th president.
Clinton was animated, loose, constantly ad libbing, varying his gestures and expression. Obama seemed more mechanical, less fluent. The contrast with the videos shown earlier of his campaigning in 2008 was not helpful.
And, perhaps unexpectedly, John Kerry and Joe Biden delivered more interesting speeches before Obama spoke.
Kerry effectively exploited Mitt Romney's inexperience in foreign policy and his omission of a tribute to the troops during the GOP convention. Biden painted a picture of Obama decisively making difficult decisions 30 paces from his own office.
The major problem with Obama's speech, however, was content: It was the same old, same old. Just as he didn't pivot on policy after his party's thumping in the 2010 elections, so he didn't pivot from his accomplishments in his first term to what different things he hoped to accomplish in a second.
He said he would pursue certain "goals" in a second term. But the goals were vague -- invest in the economy with the money we're no longer spending on war -- and in many cases rehashes of things he has said before. And there was not even the vaguest description of how specific policies might achieve these goals.
In his peroration, Obama made appeals to different core Democratic constituencies, like those made repeatedly by other speakers in Charlotte, sometimes even after 10:00 Eastern time, when the broadcast networks began their coverage.
The delegates roared again and again at endorsements of access to contraceptives (actually, free contraceptives), same-sex marriage and non-deportation of young illegal immigrants who meet certain conditions. Requiring picture identification at the polls was described as similar to beating up blacks trying to vote 50 years ago.