The most troubling number for President Obama in the new Washington Post-ABC News poll is this one: Americans say 55 percent to 38 percent that he is more of a divider than a uniter.

That's a reversal from last year, when Americans said 47-45 that Obama had done more to unite the country than divide it.

Of course, Obama also has become significantly more unpopular over that span, so it's not surprising to see his "uniter" rating drop (and in fact, both numbers have dropped equally over the past 16 months). But the uniter/divider number stings more than most other measures of Obama's leadership.

Why? Because this was the thing that put Obama on the map. During his 2004 Democratic National Convention, Obama famously intoned:

...there's not a liberal America and a conservative America; there's the United States of America.
There's not a black America and white America and Latino America and Asian America; there's the United States of America.

Fast forward to today, and the biggest divides over Obama are between conservatives and liberals and black Americans and white Americans. In fact, even on the question of whether Obama is a uniter or divider, there is huge division. Nearly eight in 10 African Americans (78 percent) say Obama is a uniter, but just 27 percent of whites agree.

That's right, Americans are extremely divided ... over whether Obama is divisive.

Of course, saying Obama is divisive isn't quite the same as blaming him for failing to unite the country. Some might see Obama as divisive just by the nature of who he is and/or think he didn't stand much of a chance to unite a very polarized country.

But regardless, people don't see him delivering on the promise and idealism of his 2004 convention speech. And with two years to go, they're only seeing him get more divisive.