Dick Cheney is surely the most visible ex-vice president these days.
But Al Gore is almost certainly the most influential.
As Congress wrestles with politically explosive issues surrounding climate change and energy, Gore is simultaneously everywhere and nowhere.
He's worked the phones to squeak a bill through a key legislative committee. He's serving as an informal counsel to allies on Capitol Hill and inside the Obama administration, as they seek to solve a complicated political equation.
The not-for-profit Gore heads is running ads in targeted congressional districts, and holding town-hall meetings across the country to drum up support for climate-change legislation. The slideshow made famous in "An Inconvenient Truth" has now been shared more than 30,000 times and counting worldwide.
The one thing the former vice president is not doing very much of: talking in public about what he's doing behind the scenes.
"Gore is playing three levels of chess on this," said Chris Lehane, a former Gore aide and Democratic strategist. "He picks and chooses his places carefully. You're more powerful when you're shaping things from the outside, from a position of your own power."
Gore has been in the news recently in his role as chairman of Current TV, which employs two journalists who are now jailed and facing trial in North Korea. The former vice president has kept a low public profile on that issue, too, even amid speculation that the State Department would send Gore to the country to help negotiate the journalists' release.
And Gore is serving as a mostly invisible hand shaping the "cap-and-trade" bill now before Congress. The bill would impose a national limit on greenhouse gases and allow polluters to buy and sell emissions credits -- a step Gore and other environmental advocates argue is critical to addressing global warming.
Democrats credit Gore with putting environmental issues on the national agenda -- and, with one of Washington's thickest Rolodexes, making sure those issues stay there through a tortuous legislative route.
"He's been a prophet on this issue," said Rep. Edward Markey, D-Mass., a co-author of the cap-and-trade bill that was approved by the House Energy and Commerce Committee last month. "Al Gore adds a luster to an issue that's indispensable."
Gore aides and associates say the former vice president believes he can be more effective as a behind-the-scenes player, rather than as the public face of legislation, or with a formal role in the Obama administration.
With a Nobel Prize under his belt, and after being the subject of an Oscar-winning documentary, he feels he can best move the process along from the outside.
"His work is evident; he is not," said Daniel J. Weiss, a veteran environmental activist who serves as director of climate strategy at the Center for American Progress. "He's being very judicious about the use of the Gore brand. It shows that this for him is about solving the problem, and not about him."
The relatively low public profile also reflects a political reality that Gore himself is aware of, associates say: More than eight years after almost capturing the presidency, Al Gore remains a polarizing figure -- and an easy target for Republicans.