Ed Miliband will face "really vicious" personal attacks during the general election campaign, according to the Labour leader's wife.
But Justine Miliband, who married Ed in 2011 and has two children with the Doncaster North MP, said she was "totally up for this fight".
"I think it's going to get worse. I think over the next couple of months it's going to get really vicious, really personal," she said.
"But I'm totally up for this fight and I thought about the reason why, and the reason is this goes way beyond Ed as an individual.
She added: "I think it's about whether decencies and principles count for something in political life. It's not just about Ed, it's about every single politician that tries to do the right thing despite personal attacks.
"If you ask me why I am up for a fight, I am fighting not just for Ed but I am fighting for a principle of decency in public life."
Miliband made the remarks to the BBC in her first major TV interview as Labour struggle to take over the Tories in the polls.
The barrister also revealed that she made a speech at Labour's party conference in 2013 to show that she was "more than a dress".
"The only reason I first gave a speech to Labour Party members at Labour Party conference was because I was so worried that by about three years in all they knew about me was a dress I wore to Ed's speech and I thought I really want to reassure people that I am in fact more than a dress," Miliband said.
The intervention comes as Labour struggle to overtake the Tories in the opinion polls with just 56 days to go before the general election.
The latest survey from YouGov, which questioned more than 1,500 voters between 9 and 10 March, put the Conservatives on a two point lead over Labour (33% vs 31%).
The study also found that Ukip were on 15% the Liberal Democrats on 8% and the Greens on 6%.