Let's look at exactly what happened in Iowa. By virtue of its peculiar caucus system, Iowa's two hundred thousand Democratic votes were reduced to 1406 votes for electoral delegates. Of those 1406, eight went to Martin O'Malley, so Sanders and Clinton split the remaining 1398 delegate votes. If it were an actual tie, each of them would have received 699 votes. But instead of a tie, two more than 699 went to Clinton, and two less than 699 went to Sanders. That's how close it was.
The real news out of Iowa, therefore, is just how razor-thin was Clinton's margin. The headline should have been: Photo Finish. Dead Heat. But that's not how the news media spun it. They like to declare winners and losers, so the headline was: Clinton Wins. And they add, as an afterthought, "Oh, by the way, it was very close."
So one might be tempted to go away thinking, "Too bad Sanders lost in Iowa." But while he lost the actual vote count by a tiny sum, Sanders won in Iowa in a larger sense. As Woody Allen put it succinctly, eighty percent of success is showing up. And Sanders not only showed up in Iowa, he showed up with class. He showed up with distinction. He made the front-runner sweat, right down to the very end. For a guy who three months ago was forty points behind in the polls, that is a win in every sense of the word.
But there's another reason Iowa was a win for Sanders, a reason only apparent when one takes a longer view. There's a very real phenomenon in politics and in life called "peaking too soon." Some long-distance runners do that, and it can cost them the race. If Sanders had won the vote count in Iowa, he probably would have peaked too soon. Everything after that would have seemed anti-climactic. Suddenly he would be the front-runner, with a series of difficult contests looming in less than a month.
Now he goes into New Hampshire strong, but not quite on top. Sanders is still in the process of gaining momentum. Now a win in New Hampshire will be a game-changer, instead of an after-thought. By losing by an eye-lash in Iowa, Sanders has nowhere to go but up. That's why Sanders's narrow loss in Iowa was a win for him.