He had Gore testify before his committee and years ago sent a message to all 3 million emails he had that gave the link to join the email list Gore was developing. He even had Clinton back his actions. Kerry did work with Boxer and he, by some accounts has her support.
Some of the possible problems are people like Feingold, a true progressive, who has voted against every climate change bill in the last year and a half. I'm sure it has to be more important to Kerry to get something passed that really does lead to something like a 17% decrease in carbon production. I'm sure that when the final bill is put together, Kerry will reach out to the the left, but I am positive that there will be angry denunciations on the left.
The fact is that Kerry has a far better record on the environment than most of the people I listed - including Gore, who is exceptional on climate change but not on other issues. In addition, the Senate passed the Byrd/Hagel resolution 4 months before Kyoto was finished. That resolution stated that they would not confirm a bill that did not include the third world. The Kyoto treaty did not meet this condition and it was not clear that much, if any effort was made to do so. Kerry, at Bali, got language that there would be constraints on the third world - though they would be different.
Now, Kerry could do the same thing - in fact, he could have done that, with Kerry/Boxer or even a more purist version of K/B. When he found it couldn't get sufficient support, he could have pushed to bring it to the floor and let it fail. He could have rallied every environmental group to call their Senators and given impassioned, brilliant speeches. But, where would that leave things - with no bill passing.
Look at the full Sanders' letter, he starts by acknowledging Kerry's tireless efforts and commitment. At this point, especially when the bill is likely not even solidified, I think this is partly an effort to have a force from that side, because there are major forces from the various energy sides. I will at least wait until the bill is out and Kerry has a chance to defend it. This is something that he and Teresa have passionately cared about for decades. I completely trust that he will not make trade offs to be better liked by the energy industry or for the personal satisfaction of having his name on an important bill, I trust that what will motivate him is getting a bill that can best be a first step to genuinely cut carbon - whether or not it hurts his own popularity.
That does not mean I will like the bill. In the current economy, it is not likely that Kerry can get the coal state Senators to vote for the type of bill that the environmental groups - and most of us would love - or even like. As Beachmom pointed out a long time ago, it may be like where Baucus was on health care. We ended up very close to the outline he developed that he thought could get 60 votes. We will need to remember how savagely Baucus was bashed. Here, the real environmental groups, have a real long history with Kerry - that might lead to some trusting that he is well meaning, but others feeling more betrayed. But, when something passes and renewables have incentives beyond what they have, a smart grid is on the drawing board and carbon really is given a price, we will likely be moving in the right direction.
Remember that on climate change, reconciliation can not be used. There was not only no language to enable it, the Johanns amendment specifically prohibited it - and Feingold, Murray, Cantwell, Webb, Warner and several other Democrats voted for it.
This was crossed posted at Daily Kos, but attracted very little attention and none from the people most knowledgeable on the issue.
http://www.dailykos.com/story/2010/3/30/7444/23084