It's not particularly difficult to work out why Gordon Brown might be promoting David Miliband for the extraordinarily named "High Representative for Foreign Affairs" job at the EU. For all that Miliband's stock has fallen in recent months, and he looks far less of a possible leadership candidate than he used to when we didn't know him so well, Brown is still anxious to get him out of the way by the time of the post-election fall-out. Miliband is a Blair protege, and Brown would prefer a clear run for his own people, who include the unlikeable Ed Balls, and the younger Miliband, Ed. So - give David to Europe, and there you go! Europe has always served the useful purpose of being a place of exile for politicians who have served out their domestic usefulness, although Roy Jenkins (who returned from being Commission President to form the SDP in the 1980s) and Peter Mandelson have proved that there can be life after death for anyone exiled there.
I'm not sure, though, that Brown needs to be quite so bothered about Miliband, as the more dangerous anti-Brown candidates are still lurking around - James Purnell, for example, would surely make a bid for the top job after the election, and as someone who freed himself from the shackles of a being a Brown minister, he would look like a fresh start.