A crowd of nearly 500 in the Library Theater in Park City, Utah, stayed on through a standing ovation and into the question-and-answer session as Al Gore — one Kentucky reporter actually addressed him as “Mr. President,” to laughs and cheers — restated his warnings about the “planetary emergency,” global warming. Mr. Gore is the star of a documentary entered in the Sundance Film Festival, An Inconvenient Truth, and all the questions were for him. The director, Davis Guggenheim, stood quietly to his left; a bit farther away was the woman who made the film happen, Hollywood Democratic power player Laurie David, the wife of comedian Larry David.

“You can quarrel with the current administration about this issue — and I do — but this is not a political issue. It’s a moral issue,” he had told a small handful of cameras outside a bit earlier, with just his graying coiff, his tank-like body and a blue blazer against the cold dusk. The Jan. 24 screening at Sundance was the world premiere of the 100-minute documentary. The film features Mr. Gore trundling through airports and, mostly, giving his famous presentation — famous to his growing circle of acolytes, at least — on the reality and gravity of climate change and the need for action. The crowd hissed when President George W. Bush appeared on the screen, and cheered loudly at the film’s punch line: “Political will is a renewable resource.” Mr. Gore had been haunting Sundance since it kicked off, popping in at the Entertainment Weekly party to chat with A- and B-list celebs, but this was the former Vice President’s big day. That morning, his new publisher, Rodale, had announced an Andrew Wylie–brokered book of the same title as the film, to be released in April. The heads of studio divisions, including Sony Pictures Classics and Paramount Classics, circled around, cementing Mr. Gore’s new status as the favored politician of the film set. His wife, Tipper, and the actress Elizabeth Shue snapped digital pictures as he made his way into the building.

And at the question-and-answer session, the reporters wanted to know about Mr. Gore’s prospects. Was the film itself covered under campaign-finance laws? Would he be endorsing another candidate for President in 2008 — like, say, Robert F. Kennedy Jr.? (It was, after all, the Hollywood press.) “I won’t be endorsing a candidate,” he said. “I am a recovering politician.” Mr. Gore — no longer Bill Clinton’s straight man, no longer the wooden, cautious candidate of 2000 — has been raising his profile through a series of impassioned speeches against the Bush administration. They began in September 2002, when he warned against the invasion of Iraq, which he said “has the potential to seriously damage our ability to win the war against terrorism and to weaken our ability to lead the world.”

He dwelled, presciently, on the risk of post-invasion chaos. That speech and others like it, along with his once-mocked warnings about global warning, have transformed him for Democrats into a kind of Cassandra, always right and always ignored. And his clear anti-war stand is in sharp contrast to Hillary Clinton’s obsessively monitored but hard-to-explain position on Iraq. Nobody in Mr. Gore’s political circle suggests, on the record or off, that he is actively planning a run for President in 2008. But the film “falls into the ‘we’ll see if that gives anything legs’ category,” said a major Democratic donor who backed Mr. Gore in 2000 and is in touch with the former Vice President’s circle of friends and allies.

First things first: Mr. Gore has said that he’s not running for President, although he said it in less-than-Shermanesque fashion. And he isn’t touching the same political bases as the half-dozen other men — oh, and that one woman — thought to be considering a Presidential campaign. He’s not massaging donors’ egos or stroking local pols in Iowa and New Hampshire. “He couldn’t be doing less,” said the donor. He’s busy warning of global warming and running an experimental new cable-television project, Current TV, whose viewer-driven, interactive model seems to be arriving at the right time.

And yet. And yet. Two prominent Democrats said that Mr. Gore didn’t discourage them when they raised the prospect of another run. And in some circles, Mr. Gore suddenly appears not just possible but unavoidable. In the new mix of power, money and ideology organized around Ms. David and Arianna Huffington in Los Angeles, in the burgeoning liberal blogosphere and among some of the former Vice President’s old friends, Mr. Gore appears the only alternative to Hillary Clinton. That is rich with irony — more than a decade ago, Mrs. Clinton was Mr. Gore’s foil in the internal squabbles of the Clinton White House.

“What has happened in Hollywood and around the country is, everybody who sees his presentation on global warming is just blown away — and it isn’t a real reach to think that he represents real vision and leadership in the White House, as opposed to what we have now,” said Roy Neel, a longtime senior aide to Mr. Gore who is still close to the former Vice President. Mr. Neel added that Mr. Gore has told him he isn’t running for President now — though Mr. Neel also said that “he would certainly be my candidate if he ran, and I think he’d make a hell of a President. “It’s no surprise that people spend a little time with him, get enthusiastic and say, ‘Damn! He’d make one fine President.’”

A weighty issue

Americans who tune back into Mr. Gore after six years of ignoring him — or, as is traditional with losing candidates, of wincing and looking away — will be struck first by his physical transformation. In the White House, Mr. Gore was the stiff, dark, hard-bodied counterpart to his soft, sunny boss, Mr. Clinton. In 1992, Fitness Magazine named Mr. Gore its “fantasy man.” In the summer of 2000, USA Today gave his dimensions as 6-foot-1, 195 pounds. But after the 2000 election, he put on weight fast. By the fall of 2002, Salon reported that he’d removed his wedding ring because it no longer fit on his finger. The ring is back, but Mr. Gore remains a soft, jowly presence.

Mark Lisanti, who writes the Los Angeles gossip site Defamer, saw Mr. Gore at a Sundance party and described him as “somewhere between husky and puffy,” and also guessed his weight at 230.

Mr. Gore’s weight gain was seen as a sign that he’d lost control of himself after enduring one of the most wrenching public defeats imaginable. Who wouldn’t binge on doughnuts after what happened in 2000? But his return to the public stage was quick, and he has been consistent, passionate and sane, and now his weight can be read another way: He’s loosened up, become himself after a campaign in which he downplayed his signature cause (the environment) and underwent embarrassing public makeovers (earth tones, public kissing).

“He has tremendous stamina — he hasn’t lost a thing,” said an old friend, New Republic editor in chief Martin Peretz.

Writing in Mr. Peretz’s magazine recently, Ryan Lizza argued that only Mr. Gore can beat Mrs. Clinton in a Democratic primary, coming at her from the anti-war left and the hawkish right of his past at the same time. There will be, he wrote, a moment for Mr. Gore to jump in: “Every primary season goes through … a period of boredom, a time when voters and pundits scour the country for fresh blood. That could be Gore’s moment.”

In a small way, that’s already happening among those Democrats who view Mrs. Clinton as too conservative on the issues and too calculating in her stances, but who see no other Democrat who can rally liberal Democrats while reaching out to, in particular, African-Americans.

“If we get to a situation where it’s Hillary Clinton and nobody has really filled the space [Mr. Gore] is currently forging, it’ll be hard for him not to run,” said David Sirota, a Democratic strategist and blogger who has worked with Mr. Gore since he left office.

Mr. Peretz said he didn’t think Mr. Gore has decided whether or not to run for President again, though he could see The New Republic — despite its differences on the war — becoming a “Gore Democrat” organ again.

“If there is a groundswell, he would be able to get back in the game,” he said. “There certainly is no groundswell for what’s-his-name Vilsack or Evan Bayh. There’s no groundswell for The Madam. This group depresses people.”

The groundswell that it would take to bring Mr. Gore into the race is already building. Ms. Huffington’s influential Hollywood-liberal Web site, the Huffington Post, has grown increasingly hostile to Mrs. Clinton, with Ms. Huffington herself attacking the former First Lady head-on and passing along the “buzz” that Mr. Gore could be the “anti-Hillary.” For Ms. Huffington, this is something of a shift: Mr. Gore wasn’t exactly her self-actualized ideal in 2000.

“You should see the stuff I wrote about him in 2000,” she told The Observer. “I was not a fan.” She wrote in “none of the above” on her ballot that year.

Now, Ms. Huffington is as enamored of Mr. Gore as she is disgusted with Mrs. Clinton. She likes his sharp critique of the Bush administration, and the fact that he offers a forceful alternative on national security. What’s more, she sees in him a transformed man — “and I know something about transformations.”

“If Gore has really been transformed the way I think he has, and if he can show it to the American people, it’s in the DNA of the American people to respond to that story, that arc,” she said.

And Ms. Huffington has turned into a force in the Democratic Party, as has Ms. David, an environmentalist, top-tier political fund-raiser and the wife of comedian Larry David.

Those two powerful women and their Hollywood friends don’t make a groundswell in themselves. But there are other elements. Mr. Gore has closely bound himself to the mother of all online liberal-advocacy groups, MoveOn.org, giving speeches under their rubric. The move conferred a kind of new legitimacy on MoveOn and has endeared Mr. Gore to the Web-based activists who sometimes call themselves the “netroots.”

The semi-declared 2008 candidates have a head start on Mr. Gore in raising money from the usual large donors. In New York, Mrs. Clinton has diligently locked up much of the traditional campaign money. But Mr. Gore is sparking interest as well. His daughter lives in Manhattan, and he stops in the city regularly. Some of his prominent financial supporters from 2000 now say they haven’t heard from him lately, but they’re more open to a Gore comeback than certain others.

“As someone who worked his ass off for John Kerry, I have to say, there’s a lot more interest in resuscitating Al Gore than there is in Kerry,” said one major Democratic donor.

Another prominent New York Democrat, Long Island publicist Robert Zimmerman, was a major donor to both Mr. Gore and Mr. Kerry.

“There’s a dramatic rediscovery, or a renewed appreciation, of who Al Gore is,” he said. “Democrats in the donor community, both nationally and in New York City, are really rediscovering him and reconnecting with him.”