Labour's decision to select John O'Farrell as its candidate in the Eastleigh by-election is being hailed  by many commentators as a game-changer. It's worth noting, however, that while there is much affection in Westminster for the author and brodcaster (best known for his 1998 book Things Can Only Get Better: Eighteen Miserable Years in the Life of a Labour Supporter), it would be surprising if more than five per cent of voters in the constituency have heard of him.
This said, not only will O'Farrell's humour and warmth endear him to voters ("There is a great deal of hard work ahead. But first I am going to the pub", he tweeted  last night), his decision to stand means that Labour, which was in danger of being ignored as the coalition parties slugged it out, will now receive far more local and national media coverage. With the polls as tight as they are (the first survey by Lord Ashcroft gave the Tories a three-point lead, the second by Survation gave the Lib Dems a three-point lead), a stronger-than-expected Labour performance could gift the seat to Conservative candidate Maria Hutchings. But having declared itself to be the party of "one nation" and having vowed to win over voters in the south, Labour has no choice but to campaign hard . Were it to finish in fourth place behind UKIP, as one poll suggested was possible, it would be a disastrous result for Ed Miliband.
Since this is a by-election, Labour has no incentive to tacitly advise its supporters to vote Lib Dem (as Ed Balls and Peter Hain did in 2010 ) but a slim Tory victory would be a reminder, as I noted  last week, that tactical voting will be an issue at the next general election. The Conservatives are in second place in 38 of the Lib Dems' 57 seats and half of their 40 target seats are held by Clegg's party. If Labour wants to prevent the Tories decapitating scores of Lib Dems, it will need to think carefully about how it approaches these contests.