When Gore testified before Congress on the issue in April, Rep. Marsha Blackburn, R-Tenn., pressed him on his financial ties to Kleiner Perkins Caufield & Byers, a venture-capital firm that has invested heavily in green technologies.
"I think it's really important that no suspicion or shadow fall on the foremost advocates of climate-change legislation," Blackburn said. "So I wanted to give you the opportunity to kind of clear the air about your motives and maybe set the record straight."
Gore laughed -- and sighed -- before telling Blackburn that the money he's earned from Kleiner Perkins helps fund his not-for-profit group, the Alliance for Climate Protection.
"Congresswoman, if you're -- if you believe that the reason I have been working on this issue for 30 years is because of greed, you don't know me," Gore said. "I understand exactly what you're doing, congresswoman -- everybody here does."
Though the hearing marked his only major public appearance on behalf of the bill, Gore has been active in pressing the issue in Washington. Last month, with the climate-change bill facing a critical vote in the House Energy and Commerce Committee, Gore phoned a few wavering members -- both liberal and conservative Democrats -- directly.
Rep. Eliot Engel, D-N.Y., said it was the first time he'd had a lengthy, one-on-one conversation with the former vice president.
"What he said to me was he thought this bill was a monumental bill, of monumental importance," Engel said. "He likened this to the Civil Rights Bill of the '60s -- years later, generations would look back and remember who voted for it, and who didn't."
Engel said he was on the fence about the bill because he felt it didn't go far enough: too many concessions to industry, and not enough funding for flex-fuel vehicles, he thought. But he wound up voting yes.
"His discussion with me factored in greatly to the decision," Engel said. "I have such tremendous respect for him. Here's a guy who was really elected president and didn't get it. He could have been bitter, angry, could have retreated into seclusion, or made a lot of money. He chose instead to take up this issue."
Gore knows the congressional dynamics better than almost anyone. Before serving in the Senate and as vice president, he sat on the Energy and Commerce Committee for eight years as a member of the House, alongside a few members who are now powerful forces in Congress, including Markey and committee chairman Henry Waxman, D-Calif.
Gore's network of associates stretches deep into the Obama administration. He's in regular touch with Carol Browner, the assistant to the president for energy and climate change who served as EPA administrator in the Clinton administration, and as Gore's legislative director when he was a senator before that.
Since he knows the major players -- and so many of those players respect Gore's role -- the former vice president can be more effective from the outside than if he was actually serving in an official capacity, Weiss said.
"If he were working inside the administration, he'd be constrained by what he can say, what the priorities are," he said.
Gore's challenge will be to keep Congress' focus on environmental issues, even while the focus turns to what may be a bigger legislative fight over healthcare.