He is gone because he lacks the support of Clinton and Obama in the other 49 states. There is no way that he can make ground with his lack of funds. Nationally Clinton was leading Obama last week in combined polls by a margin of 44.6% to 24.4%. Edwards was at 14.0% which is too far behind.
His best expected state finish was Iowa, which was one of Clinton's expected worst states. Coming into Iowa, he was a chance to win it, but he is not expected to do that well again in any other state. The Democratic nomination is between two candidates although Edwards will continue to compete for as long as he can afford it.
Its true that Hillary was leading the polls. Even going into Iowa, Hillary was a slight favourite over Obama with Edwards lagging behind. What isn't discussed some media outlets is her unpopularity with a lot of US voters. This may have been the deciding factor leading to her third placed finish in Iowa.
Another plus has been his wife Michelle. She is looked on favourably by the public and media at this early stage.
Hopefully a trend has been set for the rest of the campaign trail.
http://www.nohillaryclinton.com/