By Caroline Wyatt BBC Paris correspondent

New UMP leader Nicolas Sarkozy has resigned as finance minister

It is a move on the political chessboard that could change the face of French politics.

Nicolas Sarkozy, France's popular and ambitious finance minister, has well-known personal and ideological differences with President Jacques Chirac.

And on Sunday he took the helm of the governing centre-right UMP party.

Mr Sarkozy's election means that the dominant rightist party in France is no longer controlled by Mr Chirac or one of his loyalists.

Young Sarkozy supporters could barely contain their ecstasy as their hero walked through the crowd and they reached out to touch him in a frenzy.

It felt less like a party conference, more like the coronation of a new young king.

Waving French flags and banners, the under-40s shouted Sarkozy's name as the old guard watched on, looking slightly shell-shocked by this American-style display.

Electrifying personality

Then the man himself leapt onto the stage brimming with energy and ideas for the party's future and for France.

On a podium decked out in the French colours, Nicolas Sarkozy spoke of France as a great nation and a world power - a nation not condemned to decline but one which must move forward to ensure a more prosperous, dynamic future.

The party - or the youngsters at least - loved it.

Mr Sarkozy appears very sincere, but his vision of the world and of the future is not very clear Beatrice Gueary French journalist Profile: Nicolas Sarkozy

Nicolas Sarkozy is one of the most electrifying politicians in France today.

He is a man whose energy and enthusiasm is infectious and whose promise of a new start appeals to all those fed up with the grip of the enarques - the political elite who have long controlled French politics.

Mr Sarkozy's success so far is thanks in no small measure to his wife Cecilia Sarkozy, who is his equal in this very modern political partnership.

And she was watching on with pride.

"I'm very happy for him, very happy, and excited because I think it's a wonderful moment for him.

"He has worked for years and years, and it's the beginning of a big change in his life.

"At the moment it's president for the UMP, so we'll see afterwards what happens."

Eye on the top

The man whose job Mr Sarkozy wants next, the current president Jacques Chirac, was noticeable by his absence.

The "Sarko Show", as the French tabloids called it, will make Mr Chirac's 72nd birthday on Monday just that little bit glummer.

The new UMP leader was congratulated by Mrs Chirac

But not everyone is so enthusiastic about Sarko.

Herve Mariton is a leading MP who dislikes Mr Sarkozy's more radical ideas, such as state funding for mosques or positive discrimination for ethnic minorities.

"I'm not too confident as to where he will lead the UMP to," he said.

"I think he has too much of an opportunistic stand and in actual fact, it makes him very keen to the politically correct.

"What we need on the political right in France is NOT political correctness."

'Unclear vision'

Politically correct or not, journalist Beatrice Gueary, author of The Rebel and the King, believes the battle for the French presidency is only just beginning and that it is by no means clear that the energetic young pretender will win.

"It's a war of generations," she says. "Mr Sarkozy appears very sincere, but his vision of the world and of the future is not very clear.

"We must not forget that age is not necessarily the deciding factor in elections."

For the grand finale, there was a Pop Idol-style rendition of the national anthem by two young French women, Leila and Shirell.

And the hope expressed by Nicolas Sarkozy - that in 30 years time those here would never forget this day.