It had to happen. Towards the end of Ed Miliband's bruising BBC Radio 2 phone-in on Thursday, one caller addressed him as David. This man is not alone. At least one of Mr Miliband's staff does it too.
Three months after beating his older brother to the Labour leadership, Mr Miliband is still struggling to escape his shadow. To be fair, there have been some positive signs recently. He scored a hit with his attacks on this week's rise in VAT to 20 per cent, dubbing it "the wrong tax at the wrong time". It was a simple but effective example of what opposition is about. The Tories may have whined about opportunism, but if that is the best insult they can throw at Mr Miliband, then he is making progress.
Alan Johnson, the shadow Chancellor, muddied the waters a little, displeasing Team Miliband in a round of media interviews. He muddled up his years outlining when Labour would clear the deficit and was sidetracked into a debate about Labour's election pledge to raise national insurance contributions.
There is some tension in the air between Mr Johnson and Mr Miliband. The shadow Chancellor has staked out his own position on university funding and income tax before eventually coming into line behind his leader's policies for a graduate tax and to make the 50p tax rate permanent.
Mr Johnson's independent streak probably reflects the doubts about Mr Miliband inside his party. There's no plotting against him. It's probably more a case of a desire to be led from the front, for him to deploy against the Government the ruthlessness he showed by denying Ed Balls the shadow Chancellor's post and ousting Nick Brown as Labour's chief whip.
If Mr Miliband has shown one thing in his first 100 days, it is that he will not be rushed. "Patient, calm, confident" are his watchwords. For a self-acclaimed leader of a new generation, it seems curiously out of step with an ever-faster political and media cycle. Even some close allies realised before Christmas that it was time to put his foot on the accelerator. Although Mr Miliband had convinced his inner circle he had a strategy, there wasn't much point in keeping it secret. And many long hours were being spent discussing medium-term planning rather than joining the day-to-day battle with the Coalition.
That has changed after the belated appointment of two former Westminster journalists – Tom Baldwin as director of strategy and communications and Bob Roberts as director of news. They have begun the mission to explain the secret strategy and Mr Miliband's three-pronged approach on the economy, social mobility and new politics. After his tortoise-like start, the Labour leader is finally moving faster. He will make an important speech to a Fabian Society conference next Saturday.
Mr Miliband sees Labour's place as being in the "radical centre". Although many in his party will never forgive the Liberal Democrats for supping with the Tory devil, Mr Miliband believes there is still a "coalition of values" between Labour and the Liberal Democrats that makes them more natural bedfellows than Nick Clegg's party and the Tories. He is sincere about keeping links open to the Liberal Democrats, as he will demonstrate by campaigning hard for a Yes vote in the May referendum on whether to replace the first-past-the-post system with the Alternative Vote. That will put him at odds with at least half of his own MPs; he will portray the split as a generational one.
Mr Miliband's olive branch to the Liberal Democrats is partly out of self-interest. If the Government's economic medicine is perceived to have worked, he knows he may well need to form a coalition with the third party to have any hope of becoming prime minister.
In the short term, there will not be much love lost between Labour and the Liberal Democrats. Mr Miliband and Mr Clegg both need to win the Oldham East and Saddleworth by-election next Thursday, but only one of them can.
Mr Miliband is quietly confident of a win Labour would hail as a return to two-party politics. But there are some Labour jitters that a low turnout might yet cost it the victory it should secure on the back of the Liberal Democrats' collapse nationally since entering the Coalition.
If Labour doesn't win, then Mr Miliband's new year offensive would be stopped in its tracks and the muttering about him in his party's ranks would get louder.
A Liberal Democrat defeat, in a seat where they trailed Labour by only 103 votes last May, would inevitably increase the pressure on Mr Clegg from the doubters in his party, which is used to winning by-elections rather than losing them. A second place could be explained away as the price of power and taking hard decisions. Coming a humiliating third behind the Tories could not be and would spell real trouble for Mr Clegg. Whatever the special circumstances in an unusual by-election, his internal critics would see it as evidence that the party is heading for a meltdown at the general election.
Mr Clegg and Mr Miliband have more in common than they realise. Like football managers, party leaders are under increasing pressure to produce instant results and, by definition, they can't all be winners.