I've just returned from the conference hall, where David Miliband has made by far the best conference speech he's ever delivered. It was passionate, gutsy, thoughtful and eloquent. He joked that he had plenty of material to work with, referring to one computer file named "Saturday: version 7" and another named "Tuesday: version: 23".
Miliband was careful not to stray too far from his brief, but parts of the address were transparently lifted from the leader's speech he never delivered. He made an effective appeal for party unity and declared: "No more cliques, no more factions, no more soap opera." And, in a neat riposte to Bob Crow et al, he quoted Labour's fourth leader, John Robert Clynes, who said Labour politicians went into politics "not to practise class war, but to end it".
He described Ed as a "special person", of whom he was "incredibly proud", and, to his supporters, he insisted: "Don't worry, I'll be fine". But there was no hint either way of his intentions.
At the heart of the speech was an eloquent defence of what Miliband called "hard-headed internationalism". On Afghanistan, he said: "We're not an occupying army, we're trying to prevent an occupation." But he qualified this by reminding delegates that foreign armies never end civil wars.
And, like his brother, he promised to support David Cameron if he did the right thing. "When he takes risks for peace, we will be the first to congratulate him every step of the way," he said.
Listening to Miliband, many recalled the New Labour years when Gordon Brown would deliver a barnstorming speech on the Monday, taunting Tony Blair to outdo him on the Tuesday.
Yet there are important differences: Ed defeated David in an open and fair contest and there is still genuine warmth between the brothers.
But the younger Miliband will still have his work cut out trying to top this tomorrow.