There are three serious dangers in the debate about the stimulus package. The first is that President Obama will think too small. The second is that he will think too bipartisan. The third is that the public will be swayed by myths, such as the claim that infrastructure spending just takes too long to gear up, or that the deficit is the paramount problem. Post-partisanship will last only until it's clear that Republicans will try to wreck his presidency -- and they will try.