Politics can be a very tough business. You can make one mistake and in a few seconds the work of months or years can be nullified.
We have seen this in the last few days with Howard Dean. After more than two years of campaigning his chance of becoming the Democratic nominee for President (not that he would ever have won against Bush) ended after his speech after the Iowa result where he made a frenzied speech which might be okay for a local state official, but scared the crap out of most people who then imagined him with control over several thousand nuclear weapons.
I am in the US at the moment, and Dean is being mocked non stop on radio and TV with basically no defenders. This is what will hurt the most – losing through such an avoidable own goal. Mike Moore did similiar in 1993 with his wild concession speech which was totally misjudged.