Paul Krugman Has No Cojones

Economist Greg Mankiw criticzed the Obama administration's economic forecasts, which call for only a 1.2 percent drop in GDP this year and an average annual growth of 4 percent over the following four years, for being overly optimistic. (The better to justify his claims he will shrink the deficit).
Paul Krugman, who is an ethics-free partisan hack, blasted him for being deliberately obtuse in a blog post called "Roots of Evil."
Mankiw responded by challenging Krugam to put his money where his mouth is and bet money on Obama's prediction coming true.
Krugman has, as you would expect, not followed through.