As he exited the stage to a rare round of applause - waving to the hostile audience who had grilled him for half an hour - this happened:
What made him trip? "He slipped on David Cameron's sweat," explained the Labour leader's campaign chief Lucy Powell afterwards.
You might think she was joking, but a closer look at pictures of the Prime Minister's sweaty face suggests a politician may have actually given a right answer for once.
David Cameron struggled to keep the sweat away in a heated exchange with a hostile audience in Leeds
It could have been so much worse for Mr Miliband - he could have emulate former Labour leader Neil Kinnock's famous 'beach moment':
The night started well for Mr Miliband as he walked confidently up some steps - albeit with some guidance.
Ed Miliband is guided up the steps at the Leeds Art Gallery It all went downhill from there. At least he didn't end up on his backside though - that would have handed the right-wing press a week's worth of front-pages.
Read more: How the three leaders compared
QUESTION TIME ELECTION LEADERS' DEBATE - AS IT HAPPENED
Miliband: No deal with the SNP to become PM
The #Milistumble, as it was dubbed on Twitter, quickly became the most-talked about moment of his whole 30-minute interrogation and sparked a flurry of jokes on social media.
If he succeeds in his mission to become Prime Minister, they may have to build a ramp outside Number 10 Downing Street.
In pictures: Ed Miliband trying to look normal
The Independent has got together with May2015.com to produce a poll of polls that produces the most up-to-date data in as close to real time as is possible.
Click the buttons below to explore how the main parties' fortunes have changed:
All data, polls and graphics are courtesy of May2015.com. Click through for daily analysis, in-depth features and all the data you need. (All historical data used is provided by UK Polling Report)