Samantha Cameron has spoken of her "desperation" for her husband to triumph on May 7 - just days after Ed Miliband's wife insisted she was "totally up for" the election battle.
Mrs Cameron used an interview with the Sun to give an insight into her life with the Prime Minister at Downing Street, and praise the way he handles the pressure of the job.
But she played down suggestions that David turns to her for advice on key decisions, saying she was "fairly hands off" with politics.
The intervention came after the Labour leader's wife, Justine, gave a rare on-screen interview, arguing that her husband stood for "decency and principle".
"I think over the next couple of months it's going to get really vicious, really personal, but I'm totally up for this fight," Mrs Miliband said.
Mrs Cameron - once described by former Tory spin doctor Andy Coulson as the PM's "best weapon" - said he was a "brilliant dad and a brilliant husband".
"I am proud of my husband all the time. It's such a stressful job with a huge amount of responsibility and he does deal with it really well," she said.
"He has an amazing ability to stay calm, he's very level-headed. He tends to operate quite well under pressure.
"For me, what's brilliant is he can do that and still be a brilliant dad and a brilliant husband. I'm very grateful for that."
Mr Cameron previously said he spoke to his wife about "life and death decisions" including hostage rescues and troop deployment but Mrs Cameron said: "I don't know what he was thinking of."
The 43-year-old added: "I'm a fairly hands-off political wife. I don't get involved in the machinations at all. I don't think he takes my advice about politics. I wouldn't want him to, it would be too much responsibility for me.
"We talk about stuff when he gets upstairs, I listen to the radio a lot. As with any husband and wife you get the view of a mum."
Mrs Cameron dismissed rumours that her husband could choose to step down in 2017 even if he wins the election.
"I desperately want my husband to win the election. Obviously it's up to the British people. If he wins we'll be here for another five years," she said.
She said they attempted to keep a family-work balance by going to the cinema and taking part in a quiz night at their children's school.
"I've done my very best to keep our personal lives as similar as possible to what they were before," she said.
" For the older children when we came here it was very daunting.
"You feel very protective of your marriage and your children.
"But the children go to the same school and I go to the same job. The school is very supportive."
Mrs Cameron said the Conservative leader was good at cooking - but tidiness was not one of his virtues.
"He is a very good cook, he finds that very relaxing. Nancy's learning to cook. I'm trying to train them to tidy up as they go along but it's slightly futile," she said.
"I am quite tidy and he's not very good at picking up his clothes - newspapers lying everywhere, t hat's the other one."
Asked what Mr Cameron found annoying about her, she replied: "I'm a terrible singer. When I sang nursery rhymes to the kids, he was like 'Stop. Stop'. I am never going to be on X Factor."