Should you judge a book by its cover? France's presidential candidates certainly think voters do, and more than ever have tried to get their political message across through their image.

With unemployment and economic woes topping voter concerns, incumbent Nicolas Sarkozy has sought to change from a Rolex-wearing president with a supermodel wife to a more humble, discreetly dressed man listening to the needs of the people.

Almost conversely, Francois Hollande — the Socialist who tops polls ahead of Sunday's first-round voting and admits to a penchant for hamburgers — saw his popularity surge after he went on a strict diet, modernized his glasses, and went from baggy, shapeless suits to darker, sharper designer cuts.

Image is important in politics almost everywhere. But striking the right visual tone is especially crucial in France, capital of the luxury and cosmetics industries, home to the world's premier fashion shows, and whose Parisian salons have set global style trends for centuries.

And with candidates' every public move now under scrutiny of smart phones and Twitter, observers say maintaining a good presidential image in 2012 is harder, and more paramount, than ever.

Hollande, described six months ago by satirists as an indecisive marshmallow, summed it up best himself, declaring in his February autobiography that: "Style makes the man, we say. Style also makes the president."

"People here are incredibly critical and demanding of the image of the politicians ... You can't be too drab, and too showy is seen as vulgar," said Rebecca Voigt, a Paris-based fashion writer.

As he campaigns, Sarkozy has been trying to shed the much-lampooned perception that he courts the rich in a country where wealth is meant to be discreet.

Five years ago, on the night of his election victory, Sarkozy wined and dined at Paris' exclusive Fouquet's restaurant and then vacationed on a French billionaire's private yacht.

But this year, Sarkozy declared he would be "a different president." He allowed himself to be personally approached at rallies, and modified the way he dressed.

"Gone are the severe black suits with patterns, replaced by light blue shirts, navy blue jackets and ties with hardly any decoration," says Diane-Monique Adjanonhoun, a political marketing strategist. "This is intentional, blue is a color that makes people think you're more open."

But will this change of image convince?

Voigt doesn't think so: "He came into office with a Rolex, the ultimate symbol of money. Though he's changed his watch to a slightly less showy Patek Philippe, that unpopular showy side is not forgotten. (U.S. President) Barack Obama's very calculating in how he dresses, he looks so quiet and everyday. Obama would never wear a Rolex, with people suffering the financial crisis."

Footage circulating online of Sarkozy removing his expensive gold watch before speaking to voters at a rally Sunday in central Paris did not go down well: Was it due to fear of theft, French media asked, or of recalling the "bling bling" period the President had been trying to bury?

Controversy has also courted Carla Bruni-Sarkozy: French media drew comparisons between the French first lady and Marie Antoinette earlier this year, when she declared on France 2 television she and her husband "are modest people."

However, the millionaire former supermodel and singer has indeed dressed down her image — and, some say, with political gain. In March, she was featured on the front cover of Paris-Match magazine clutching her new baby Giulia in a baggy gray cardigan, flat UGG boots and no make-up.

"She's showing she is normal, and this is sure to win him votes," says fashion consultant Isabelle Dubern.

In the Socialist camp, many were concerned that their candidate, Hollande — a middle-aged man viewed more as manager than visionary — was not considered sufficiently presidential.

That was before the crash protein-based Dukan diet that reportedly saw him shed 15 kilograms (33 pounds) by cutting down on wine, cheese and chocolate. Hollande is now slim enough to don the more fashionable, fitted and structured jackets more associated with Elysee Palace residents.

"It might have been unconscious but French people saw his round face and did not think of a leader," said Adjanonhoun. "He dressed like he was from the country with cheap material. Now he has completely changed."

Hollande's language has changed, too, more often saying "myself, I," which some observers say signals self-affirmation and a growing confidence that's perceived as presidential.

His unmarried partner Valerie Trierweiler, a well-dressed and impeccably coiffed political journalist, is also seen as an asset to the presidential ticket.

Other candidates, too, have pushed the style button to make statements about their politics.

Marine Le Pen, the leader of France's extreme right National Front and daughter of party founder Jean-Marie Le Pen, has helped soften the anti-immigrant party's image.

Being a woman — and at a relatively young 43 years old — she's seen as less offensive than her aging, hard-line father. Her campaign poster shows her looking directly forward, relaxed and with an unforced smile.

"She has succeeded in seducing many with her natural expression, and even the wrinkles she allows on the poster. She has a navy blue jacket on a sky blue background, which is soothing but also symbolizes the color of the party," said Adjanonhoun.

Another perceived style coup came from the firebrand left wing candidate Jean-Luc Melenchon. His trademark fashion statement is a red scarf or red tie — representing not only his leftist stance, but drawing a direct link with the only Socialist ever elected president in modern France, Francois Mitterand, who also wore red.

The Greens Party candidate, 68-year-old Norwegian-French Eva Joly has been the source of mockery as well as admiration for her eccentric spectacles. For many weeks she sported some flashy red glasses, only to swap them for a color perhaps more tasteful to her political convictions: a more ecological-looking green.

Whatever the outcome of the first round of the presidential poll Sunday or the second round May 6, political author Valerie Domain says that in France, while "a politician is meant to have ideas and conviction, the first (priority) is what you wear."