Why Was McChrystal's Report Leaked?

Joe Klein wonders why Gen. Stanley McChrystal's confidential report on Afghanistan to Defense Secretary Robert Gates--in which he states that not sending more troops "will likely result in failure"--got leaked to The Washington Post's Bob Woodward. While everyone expected to get some sort of picture of McChrystal's Afghanistan outlook, Klein surmises:

What's provocative about the report is that it was leaked to Woodward--a serious breach of conduct by someone, possibly in the military (or a supporter the military's position). This was an effort to lobby a quick decision on troop strength--which the military wants, so that it can begin planning the 2010 fighting season in Afghanistan. But a quick decision is not a good idea right now.

It's worth pointing out, however, that the leak helps the White House, not just the military, if it's decided it must follow McChrystal's advice. The left's resistance to America's commitment in Afghanistan has grown since 2008, and, given the deference President Obama has shown his generals so far, and since we're coming off several years in which Democrats painted Afghanistan as the justified war (as opposed to Iraq, the unjustified one), it wouldn't be surprising if Obama believes he needs to follow his new commander's advice, at least in the first go round. Leaking McChrystal's blunt words gives cover to anyone wishing to follow his recommendation.