Barack Obama has a 69 percent approval rating, at least with people who use Twitter. And it turns out, the people who use Twitter are disproportionately black.

The latest NBC/Wall Street Journal poll finds that 14 percent of African-Americans report using Twitter — double the percentage of white Americans who say they tweet, and nearly twice the 9 percent figures for Hispanics and Americans overall.

That could be part of the reason Obama has such high approval ratings among the Twitterati. The president has a 46 percent approval rating in the NBC/WSJ poll, but that figure jumps to 69 percent among Twitter users, though it ticks up to just 48 percent among social media users overall.

The source of the president’s troubles are those who are not connected. He scores just a 43 percent approval rating among people who don’t use social media at all. And the president’s approval rating among Facebook users is 47 percent, meaning those users may be the most broadly representative of the online U.S. population.

Obama job approval
Overall: 46 percent
Among social media users: 48 percent
Among non-social media users: 43 percent
Among Facebook users: 47 percent
Among Linked-in: 52 percent
Among Twitter users: 69 percent

Use of social media by ethnicity and type

Facebook
All: 55 percent
African American: 44 percent
White: 55 percent
Hispanic: 57 percent

Linked-in
All: 10 percent
African-American: 5 percent
White: 11 percent
Hispanic: 9 percent

Twitter
All: 9 percent
African-American: 14 percent
White: 7 percent
Hispanic: 9 percent

When it comes to a match-up between Barack Obama and Mitt Romney, Obama beats Romney by a hair overall, leading in the NBC/WSJ poll by 47 percent to 45 percent — a statistical dead heat. Obama leads by three points among social media users, 47 percent to 45 percent, and by one point among the non-sharing inclined (47 percent to 46 percent.)

But when you look at the specific social media types, it becomes clear why the Obama campaign has place such a premium on social media outreach.

Obama beats Romney 47 percent to 44 percent among Facebook users, by a much wider 52 percent to 38 percent among those who use Linked-in, and by a whopping 56 percent to 32 percent among Twitter users.

The pollsters didn’t explore whether the overindex of blacks among the Twitter-inclined feeds Obama’s popularity there, but a correlation would not be surprising.