Matt Yglesias is exactly right about the vacuity of the Broderite Bloomberg project ("You could imagine a third party campaign based on Ron Paul's brand of libertarian nationalism, but all Boren, Bloomberg, et. al. have are platitudes"). It's all form without substance, a desire for some mythical 'bipartisanship' with no idea of either what that means substantively or how we get there.
One other thing struck me, though. The practical justification for third-party candidates is generally dissatisfaction with the existing candidates. There is plenty of dissatisfaction this year...with the Republican candidates. Most Democrats are actually pretty happy with their options (rightly or wrongly). Like them or not, the top Democratic candidates are all solidly competent people with serious ideas about substantive issues; the Republicans, not so much.
So in looking around and saying there are no good candidates, these 'bipartisan' wannabes are acting as if the Democratic field were as shallow and stunted as the Republicans. Or, more precisely, they're simply going on the assumption that a Democratic president isn't an option worth considering.
And yes, that includes the candidate who says a lot of the same things they're saying.
Just one more example of the visceral loathing the Broderites have toward the Democrats.