In a much-noted interview  with me in this week's New Statesman, Tim Farron, the Liberal Democrat president and the standard bearer of the party's left, lavished praise on Ed Miliband. He told me: "I really like Ed Miliband, so I don’t want to diss him. I don’t want join in with the Tories who compare him to Kinnock."
He added: "I think he is somebody who is genuinely of the Robin Cook wing of the Labour Party, from their perspective what you’d call the 'soft left'. Somebody who is not a Luddite on environmental issues, somebody who’s open minded about modernising our democracy, somebody who’s instinctively a bit more pluralistic than most Labour leaders and a bit more internationalist as well."
In what some Lib Dems saw as a gibe at Nick Clegg, he also remarked: "For all that I think he could have done a lot more on the AV campaign, he did at least have the backbone to come out and back it. He wouldn’t share a platform with Nick [Clegg], so he ended up with me, poor thing. I like the guy."
In his speech at the conference launch rally tonight, Clegg was due to issue a coded criticism of Farron. The version of his speech emailed out to journalists beforehand included a passage in which he said:
"Now I know that some people in our party don’t like us being too nasty to Labour, so in the spirit of cross-party cooperation, I’m going to help them make a start. If the Eds are watching, here is the first thing they should do to win back the trust of people. Apologise."
The line highlighted above was an obvious reference to Farron's comments on Miliband ("I don't want to diss him"). But in the version delivered by Clegg it was amended to:
"But let's not be too nasty about Labour."
For the sake of party unity, Clegg retreated from an attack on his most likely successor as leader - and wisely so. When Farron signals his preference for Labour over the Tories, he speaks for most Lib Dem members. As a recent Liberal Democrat Voice poll showed , by 55% to 18%, members would prefer a post-2015 alliance with Labour than one with the Tories. If Clegg is to retain the faith of his activists, he needs to avoid giving the impression that he would rather form a second coalition with David Cameron than open the door to Miliband.