I watched Gore's documentary again and the answer seemed obvious, he needs to run for President. The entire premise of the movie, a man and a mission, city by city, making the case, giving the issue exposure. If you don't fixate on the question of winning or losing, it seems like a no-brainer that Gore's cause is best served by a high-profile run.
At the very least, Gore in the mix demands that the issue of the environment doesn't get lost in the primary debate. The pre-occupations with Iraq and terrorism set the stage for a Democratic race that puts the environment as afterthought. Of course, we will hear some ideas, desperate language, urgency, but only Gore will bring serious debate, possibly forcing people to go farther than they would otherwise. Gore advances the agenda, speaks to wide audiences, has the ear of the media, all of which serve his "mission".
I honestly think Gore could win, it is a realistic scenario. Primary voters tend to be more "progressive", this constituent a natural ally for Gore. Gore is already the online darling, ala Dean, minus the shortcomings. Gore is polished, newly passionate, articulate and intelligent on every issue. Gore entering the race isn't predicated on winning, but it could happen, which affords him ultimate exposure to mold the American political debate. Al Gore as President, the environment has arrived.
Gore's cause is best served by a run, it gives him all the elements he needs to make the case. If Gore fails in his bid, he may still have exerted some influence in pushing others and raising the profile. A quick scan of the other contenders, you really don't sense a passionate advocate that really understands the need for bold, radical change. The environment needs Gore to sharpen his opponents and possibly capture voters imagination. All the polling tells us, that despite no intention of running, Gore still has sizable support- that is independently impressive. In other words, there is an audience and Gore's conviction would only expand it. I see Gore running as a win-win, the only unknown the degree of influence.