Politics, like life, is characterized by change, contingency, unpredictability, and indeterminancy. Jay Cost makes this point well with regard to the Iowa Democratic caucus:
A poll of Iowa Democratic caucus goers does not really mimic the process in which they participate. In a general election - you go into a voting booth, select your first choice, leave the booth, and drop the ballot in the box. And so, a poll that asks you for your first choice and then moves on to other questions does a reasonably good job of mimicking the act of voting. However, this is not the experience of Democratic caucus goers. Iowa Democrats begin by standing in an area designated for their first choice candidate. Then, for thirty minutes, they either persuade or are persuaded by others to switch their choices. At the end of the half hour, electioneering is halted and caucus officials count the number of supporters that each candidate has. Candidates who have less than 15 percent or 25 percent are deemed not to be viable. And so, another thirty minutes for electioneering is once again granted. The supporters of nonviable candidates must find new candidates to support, team up with supporters of other nonviable candidates to make their candidate viable, or abstain.
Cost concludes that the only thing we can say for sure about the Iowa Democratic caucus is that the eventual winner will be either Clinton, Obama, or Edwards. In my view, that's an accurate conclusion.