It was the moment the mask fell - but still the mascara stayed put. An exhausted Hillary Clinton, ground down by the gruelling campaign pace and ceaseless media focus on her appearance, was thrown off guard by the sisterly warmth of the question: how do you do it?

On Tuesday night as she appeared beaming and radiant before her hollering supporters in Manhattan, the question was back on the lips of even the less empathetic observers: how does she do it indeed?

Mrs Clinton's flawless appearance at the New Hampshire debates kicked off a flurry of Botox and plastic surgery rumours. Her campaign has denied the surgery claims but remained silent on the Botox issue.

Her latest federal campaign spending reports revealed that she spent $7,500 on voice and drama coaching in October in preparation for the debates and primaries.

The secret weapon that night, however, was CNN's make-up artist Kriss Soterion, who gave Mrs Clinton a fresh look that she has stuck with ever since. “As I started to do her make-up her assistant held up a bright-red lipstick,” Ms Soterion told The Los Angeles Times.

“My gut just said 'no way'. It looked too political, the lipstick equivalent of a red necktie. What I wanted to do was soften and feminise her look and make her someone women can totally relate to. She is already powerful and

I didn't think she need to have powerful make-up to get her message across.”

Ms Soterion mixed up a new, plummier colour for Mrs Clinton that she dubbed “Debate”. But it was the dewy, no-wrinkle look that really caught people's eyes.

“I must have gotten a thousand e-mails about that afterwards,” Ms Soterion said. So did Mrs Clinton. “She just said: 'Kriss, the reviews are really good, I'm going to have to adopt you'.”

Unfortunately for Mrs Clinton Ms Soterion is already under contract to CNN so she was unable to poach

her for her campaign. Instead there are rumours of $1,000 (£500) haircuts and a $2,000 make-over from Barbara Lacy, a top Hollywood make-up artist.

It is a far cry from the lank hair and milk-bottle glasses from the early days of her marriage that set the tone forb a woman who cared more about what she had to say than what she looked like.

Mrs Clinton has learnt the hard way, however, that poor grooming can distract from the message just as surely as a stunning exterior. As First Lady she was endlessly derided for her ever-changing hairstyles as she tried to settle on one that worked for her. An awkward Alice band arrangement was an acknowledged low point.

Now she has found a hairstyle that hits the right balance between smart and soft. Even she jokes of it as a metaphor for the more stable political platform she has settled on after years of experimenting with her policy belief.

All of which is less to enhance her appearance than remove her appearance as a talking point so that people will listen instead to what she has to say. Still, everyone is talking about how fabulous she looks in this most arduous of races. Aides say she made it through the toughest part of the campaign, in New Hampshire, with as little as three hours' sleep a night.

Her opponent, Barack Obama, is said to eat healthy lean proteins such as chicken and fish, work out on elliptical machines every morning and play basketball. Mrs Clinton admits however that she rarely finds time to work out and disclosed that her new year resolution was to shift some weight.

The Kriss Soterion makeover

Step One Hydrate the skin

Step Two Apply a retexturing cream to hide imperfections and follow with a liquid foundation with light-reflective properties to create a natural glow

Step Three Blend concealer around the eyes to hide signs of tiredness, then add blush to highlight and colour the cheeks

Step Four Never underestimate the importance of matching your eye shadow and eyeliner to your outfit and skin tone. Adapt the colours you use to your outfit

Step Five Ditch bright red shades in favour of lipstick and lipliner in softer plum tones

Re-create that look at home

Light Diffusing Liquid Foundation, SPF8 £9
Camoufleur Mineral Concealer £9
Loose Mineral Blush £9
Indelible Waterproof Eye Liner Pencil £7
Loose Mineral Shadow (creaseproof) in “violet illusion” £7
Eyeliner in “charcoal” £5
Supreme Mascara (smudgeproof) £6
Lip liner in “delice” shade £5
“Debate” lipstick (the exact mix used by Senator Clinton on debate night) £7.50

Total £64.50

Sources: Times archives; krisscosmetics.com

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