This Jonathan Chait post is almost completely wrong about "you didn't build that."
The key thing is that Obama is angry, and he’s talking not in his normal voice but in a “black dialect.” This strikes at the core of Obama’s entire political identity: a soft-spoken, reasonable African-American with a Kansas accent. From the moment he stepped onto the national stage, Obama’s deepest political fear was being seen as a “traditional” black politician, one who was demanding redistribution from white America on behalf of his fellow African-Americans.
These are two separate points, and the first one is dead-bang wrong. Did Obama slip into a black dialect during that speech? Gosh, if only we had some other video of Obama talking about roads and bridges in a black dialect. Hang on -- we do! It's from the 2011 CBC dinner.
Obama's talking to a black audience about infrastructure, playing on the widely-expressed black opinion that Obama has it rougher than any other president. "Suddenly, Obama's proposing it -- what happened?" he says." What happened? Y'all used to like to build roads? Right? What happened? Rev., you know what happened? I don't know! They used to looooove to build some roads!"
Compare that to the Roanoke speech.
A little loose, but nothing like the CBC speech. Chait's second point is much stronger, because there is a sub rosa fear that Obama is redistributing wealth from "job creators" to shiftless food stamp-users. But the "black dialect" thing? No. Obama was making a point lots of liberals make, and in order to weaponize it, Republicans clipped the part that sounded "anti-business." It had nothing to do with vocal intonation.