French President Nicolas Sarkozy's marriage to Carla Bruni, an Italian-born heiress and ex-supermodel long considered among the world's most desirable women, was touted as a coup for the French leader. But the author of “Carla: A Secret Life” – an unauthorized biography chronicling her transformation from an allegedly tempestuous man-eater into an apparent meek, model spouse – suggests Carla Bruni-Sarkozy has become something of a political liability for her husband. Besma Lahouri says Bruni-Sarkozy's alleged rivalry with Michelle Obama has strained relations between the French and US presidential couples, and her image of distant, well-heeled perfection has kept her at arm's length from the French people. At a time when the conservative president's popularity has plummeted, and he is being criticized for raising the retirement age and cracking down on Eastern European Gypsy immigrants, having a more accessible first lady might soften his image, she said. “The French don't know their first lady, and her worries seem to them very far removed from their own,” Lahouri said Tuesday, a day ahead of the book's release. All the French have seen of Bruni-Sarkozy of late, Lahouri said, is footage of her with the Queen of England and other dignitaries, picture-perfect in Christian Dior skirt suits with marching hats, shoes and handbags. Once regarded as a poster child of the “gauche caviar,” France's moneyed progressives, Bruni-Sarkozy “turned her back on her political convictions” following her 2008 marriage with Sarkozy, a tough-talking conservative, Lahouri said. “Suddenly, the Carla Bruni of yesteryear, who was free and spoke out, no longer existed. You never hear her publicly stand up in (Sarkozy's) defense, either.” Lahouri added it was precisely this contrast between the outspoken top model who appeared to revel in the glow of flashbulbs, living out a series of love affairs with rich and famous men in the spotlight, and the demure first lady with her sensible flats and downcast eyes that initially piqued her curiosity. Lahouri says Bruni-Sarkozy is “a chameleon,” someone who has “trained herself to be a formidable actress.” “She is a very foxy woman – I choose the word ‘foxy' over ‘clever.' In fact, very foxy.”