There is nothing in the British constitution which says that Prime Ministers and party leaders have to put pictures of themselves, their wives and their children on the Christmas cards they send out – though you would not think so, from these images.
There have even been Prime Ministers who did not assume that their mugshots were the perfect way to brighten a mantelpiece during the festive season. Gordon Brown sent Christmas cards decorated with cartoons or kids' drawings. John Major used an austere image of Downing Street illuminated by Christmas lights. Clementine Churchill would use illustrations of Winston's paintings.
But the Christmas card selfie has a long history. It certainly goes back at least to 1981, when Margaret Thatcher posed in a Lincoln green suit with padded shoulders alongside Denis, with a folded handkerchief in his top pocket, in front of a Downing Street fireplace. They at least kept their grown-up kids out of it.
This year, all three party leaders have chosen photographs that remind us what sweet family guys they are. David Cameron has previously gone in for images associated with summer, such as the Olympic torch, which were cheerful enough, if a little out of season. This year, he has gone retro, with a back-and-white photo of himself, Samantha, and their three-year-old daughter Florence.
But why only one child, when they have three? The other two are aged nine and seven, and assuming they are like normal nine- and seven-year-olds, they may have been upset at being ignored while Florence got all the attention.
Ed Miliband has also gone in for a standard politician-as-family-guy image, a shot taken while he and Justine were out on the beach with their sons. To give the couple their due, this year's Miliband Christmas card is less awful than last year's, and they have remembered how many children they have got.
Yesterday, Nick Clegg was the last of the party leaders to offer his Christmas card for public inspection, and was immediately proclaimed the runaway winner. The plaudits were not awarded for his stock image of husband and wife, Nick and Miriam, on an ugly, striped sofa against a blank wall, which would have been the worst of the leaders' Christmas cards by a margin if left untouched. What appealed to the pundits was the creative manner in which a dull, homely image had been defaced by the couple's children Antonio, Alberto and Miguel.
Using an iPad, they gave their mother a reindeer's antlers and red nose, and their father a Father Christmas hat, white beard and bright red sock. A Christmas tree was added, and a message on the wall says "Happy Christmas".
It was a very clever piece of self-promotion by Nick Clegg, which tells you that not only is he a family man, but he has smart kids and he is laid back enough to allow them to indulge their creativity.
It could be a long time before the Liberal Democrats pull such a clear victory again. µ