Steve Kornacki isn't ready to write Bloomberg off just yet:
[I]f, come early '12, the economy is still stuck in neutral and the GOP is poised to nominate a polarizing, Palin-ish nominee, there will be ... room -- at least initially -- for a third-party candidate. In that environment, Bloomberg might fare better than 11 percent. When Perot's name first began circulating in late February and March of 1992, he barely cracked double-digits in national polls; but the idea of a third option quickly caught on, and by May he was leading Bush and Clinton in three-way polls. Bloomberg is more broadly known now than Perot was in early '92, but plenty of Americans haven't yet formed an opinion of him -- so he does, at least potentially, have room to grow.
Insofar as Americans want a third party candidate, they want one who will tackle issues that both parties are, in Washington, to their left on -- immigration, spending cuts. And Bloomberg is to the left of Congress on those issues. So why support him?