Faced with the possibility of having to run against him, few have dared reject outright his ideas, which include introducing a steadily increasing carbon tax and appointing a deputy prime minister for sustainable development.

Socialist candidate Segolene Royal and others have said they will sign his "ecological pact", a pledge to put the environment at the heart of public policy, and conservative frontrunner Nicolas Sarkozy signed on Friday.

But they have stopped short of endorsing all his ideas, and whether the winner of next year's election will do more to protect the environment remains to be seen.

"To them (Sarkozy and Royal) the pact is certainly just a scrap of recycled paper, and if they win, they will create neither a carbon tax nor a deputy prime minister in charge of sustainable development," weekly L'Express said.

Hulot says it is up to politicians to make it pointless for him to run, by embracing the environmentalist cause, but he has not yet decided whether they have done enough. He is expected to announce in the coming days whether he will run for president.

With his slender frame, boyish looks and preference for jumpers over suits, Hulot does not seem cut out for the tough world of political campaigning, but his popularity is such that if he ran, he would steal votes from all the frontrunners.

The former adviser to President Jacques Chirac is, however, likely to steal slightly more votes from the left.

GREENS DWARFED

Since launching his pact in November, he has overshadowed France's main environmentalist party, the Greens, and their candidate Dominique Voynet, who polls show has the support of around 1-2 percent of voters, to Hulot's roughly 10 percent.

"The Greens have been robbed," said Daniel Boy, research director at Sciences-Po university.

"They feel that the environment has been stolen from them."

After polls suggested Hulot was far more popular, Greens veteran Voynet, who has helped mould her party into a left-wing movement, asked Hulot in an open letter to join forces with her.

But he rejected his former ally's advances.

"You chose politics, I chose another path," he said in left-wing daily Liberation.

"What I am doing is neither on the right nor on the left, or even in the centre," he added.

By choosing to address mainstream politicians, Hulot has steered clear of fractious French environmentalist politics, in which several different parties have produced a total of at least four candidates for president.

While even Voynet, a former environment minister, has received limited media attention, French newspapers and magazines have splashed Hulot across their front pages, digging up pictures of his adventurer past as presenter of 'Ushuaia'.

French daily Le Parisien asked: "What use are (other) environmentalists?" and said a wave of "Hulotmania" had swept across France.

REAL CLOUT?

"Of course I'm disappointed by our ratings in opinion polls today," prominent Greens politician and deputy mayor of Paris Denis Baupin told Reuters this week.

"We always have difficulty, and have done since the Greens were founded, getting people's sympathy for our proposals to equate to sufficient credibility for voters to place a Greens ballot in the box," he added.

For all the public interest in his bid to put the environment at the centre of French politics, Hulot too may fail to transform sympathy into political clout.

"When you ask people what the biggest problem is today, it's far from being the main issue. It might rise but it is still far behind. It is still unemployment, security, purchasing power," Sciences-Po's Boy said.

But Hulot, who for years captured millions of people's attention by climbing, canoeing, paragliding, and even vomiting in a Russian fighter jet, has forced politicians to take note or risk losing a slice of their support in a close-run race.

"They have all bought his merchandise," Boy said.

"They have to make him happy."