2. Vegans: Yes, Al Gore is a vegan these days. (Livestock cultivation is terrible for the environment.) Bill Clinton is an almost-vegan. What's going on with the Clinton administration alums, anyway? But André 3000 was a vegan, too, and despite the vegan lobby's best efforts, Outkast isn't what it used to be. So we can rule that out.
3. The Climate-Change Community: Quick—name a prominent global-warming activist who's not Al Gore. Tom Steyer? Bill McKibben? It's hard to argue they compete with the former vice president. Even with An Inconvenient Truth nearly a decade in the past, he remains the most visible figurehead for the movement. While there are some signs of positive change for activists, like new rules implemented by the Obama administration, it's never enough when you see global catastrophe on the horizon. As Gore's friend Reed Hundt told The Times, "nobody wants that job," but Gore is the incumbent and can't give it up until someone else takes it from him. And his new message of hope—rooted in the sinking cost of renewable energy—is more palatable than proclamations of doom.
4. Climate-Change Skeptics: It's important for a movement to have a leader, but it's also important for the opposition to have a villain. For climate-change skeptics, Gore's name remains a potent (if nonsensical) punchline. Senator James Inhofe, who chairs the Senate environment and public works committee, is a ringleader of this group. (He's the one who held a snowball up on the Senate floor as proof that climate change isn't happening.) The Oklahoma Republican is delighted to be able to make statements like, "Al Gore’s immense wealth is largely due to his shameless and incessant promotion of the liberal global warming agenda."
5. A Strange Coalition of Democrats: But why the calls for a third Gore run for the White House? For one thing, more Democrats are starting to get worried about Hillary Clinton's 2016 campaign. Some of them think that Clinton is in serious trouble from her email scandal, or that she's simply not prepared to run a real campaign for president. (If the rap on Clinton is that she's a candidate of the past and is too out of practice, it's hard to imagine Gore is the answer.) Others simply think she, and the party, would benefit from having a contested primary rather than a coronation.
And Gore appeals to a strange, wide swath of the party. He has links to the moderate Democratic Leadership Council types who brought Bill Clinton to office. More recently, he's built strong ties with the party's progressive wing. But he's also a wealthy businessman, wealthier than Mitt Romney, able to speak the language of commerce. Ezra Klein suggests he could shift the focus of a campaign away from income inequality and toward the environment. And joke all you want about "inventing the Internet," Gore has remained engaged in tech issues, from his 2013 book to SXSW.