Stoller's right, and the problem for Democrats is that the spectacular failure of the Obama presidency (at least thus far) presents them with two distinct threats from two distinct groups that are essential to their party's long-term survival: Young people, and African-Americans.
Young people came out and voted for "hope and change" in 2008, and are now reaping the whirlwind in the form of massive unemployment. As it turns out, the Obama presidency is disillusioning them both with Big Government and with the Democratic Party, likely -- at least in some cases -- for a lifetime.
As for African-Americans, that group has long been a linchpin of Democratic electoral hopes. So when people like Stoller delicately raise the question of whether it might be smarter to replace Obama on the ticket (or have a mainstream Democratic primary competitor), it's crazy to think that idea will go anywhere. That's because an intraparty coup against the President will insult and infuriate African Americans -- and be attributed to racial animus, even though it would have nothing to do with race (which might be an instructive lesson on how conservatives are treated on a regular basis) -- thereby threatening the very core of the Democratic coalition.
But it's hard to feel sorry for the Democrats, who are indeed trapped in a very sorry situation (at least for now). That's because they were all too willing to exploit the hopes of young people and bask in the glow of moral superiority when Barack Obama was riding high. Now, they're seeing the downside.