Why did senior Tory MP Tim Yeo make such a conspicuous bid to support Heathrow's third runway? The idea is ruled out in the Coalition Agreement, and it is politically impossible for the government to take forward. Such a bid can only weaken the government and David Cameron, the Tory Prime Minister. Rather than indulge in conspiracy theories, I prefer to think it is because most MPs, who are elected in safe seats, and the business lobby advisers, don't understand how elections are won and lost.
Mr Yeo made his bid in an article in the Telegragh. After going through the familar arguments put forward by lobbyists, he appealled to Mr Cameron to change the government's stance, by asking himself "whether he is a man or a mouse". The change could be a turning point for the government, he said, giving it a sense of mission amidst a lacklustre economy.
Heathrow's operator, BAA, and principal user, British Airways, have been campaigning for Heathrrow's expansion for many years, trench by trench. It seemed that they had lost this latest bid when the Coalition was formed in 2010. But they didn't give up, and have kept their lobby efforts going. The results are quite impressive. Grudgingly, general public opinion seems to be coming their way, amid a deluge of supportive newspaper stories. It has become a totem issue for the political right, desperate for ideas that will both expand the economy and keep public expenditure down. Mr Yeo is one of a series of Tory MPs that have publically come out in favour.
But scepticism runs very deep here in west and southwest London, where we endure continuous intrusion from air traffic. Each victory won by BAA (to date mainly over new terminal buildings) has been bitterly contested. We have seen the smooth reassurances offered in one bid quietly buried in the next. There is no trust left in BAA and BA. And amid the swathe of hotly contested marginal constituencies in the airport's shadow, the importance of the issue has only risen. This is what forced the Conservatives to oppose the new runway before the 2010 election. The area is also a stronghold for the Liberal Democrats, who have picked up on local opposition to Heathrow expansion from the start.
It is this last that is the political key for the government. Liberal Democrats are a beleaguered species since they joined the Coalition. Hopes that being in government would add to the party's credibility are fading fast, as local election results show a grim picture. A very difficult election is coming up. Here the party's objectives will be to hang on to what they have as best they can. Those local lection results show that the party can still benefit from an incumbency effect. South west London is one of the key battlegrounds, with four Lib Dem seats to defend, and a fifth Tory seat, Richmond Park, a marginal that the Lib Dems could win back. The party simply cannot afford to support Heathrow expansion. What's more, the evident Tory backsliding on the issue is one of the very few shafts of light for Lib Dem campaigners locally. If the Tories drop their opposition to it in their next manifesto they will be bring out the champagne in Lib Dem HQ.
Which makes the fact that Mr Yeo and others are upping the ante very curious. This is an existential issue for the Lib Dems, so they will veto any change of government policy - never mind that the Tory Transport Secretary Justine Greening also has a seat under the Heathrow flightpath and has campaigned vigorously locally against expansion. Politics is supposed to be about the art of the possible.
What might the explanation be? One popular theory is that it is about Mr Cameron's leadership of the Tory party. The Tory right are fed up with him, and would like him to be replaced. But to do it like this is surely suicidal - we only have to see what happened to John Major, the last Tory Prime Minister, who also had to deal with backbench discontent. The result was 13 years of uninterrupted Labour rule.
It may simply be a long term plan to ensure that Heathrow expansion goes ahead. This is surely what BAA and their advisers have in mind. If they can get the Tory party to change its mind at the top, and the Tories win the election without a few of those London seats, then bingo! They had already persuaded the last Labour government to press ahead. But this is a herding cats strategy. If they persuade the Tories to change their mind, the chances are that Labour will come out against, so that they can win back a few of those marginals in south and west London. The result of the that election could be very tight, so you don't just wish away a few seats here and there for the sake of a project like this.
Personally I think it is naivity. Some on the Tory benches have spotted that if the Conservative backbenchers are behind a government policy, and you add in the Lib Dem payroll vote, who are bound to support any Coalition compromise, then it is enough for legislation to pass, even if all the Lib Dem backbenchers rebel. So all you have to do is ram a policy past the top Coalition policy process, and you've won. This strategy worked for George Osborne when he wanted to reduce the top rate of income tax - which he did in this year's Budget in exchange for a series of policy concessions, now long since forgotten. He had similarly been told this was politically impossible. This is reinforced by the belief that the Lib Dems will not bring the show down because they are afraid of an election.
But that ended badly. Mr Osborne's Budget, including reducing the top rate of tax, is now seen as a politcal distaster. It did nothing to boost investment and growth, as the Tory rhetoric and "Business" claimed it would. And as the next election looms Lib Dems are increasingly focusing on how to hold onto their parliamentary seats. It's one reason why they jumped at the chance that Tory backsliding on Lords reform gave them to ditch the new constituency boundaries - which they had come to realise would make things very difficult for them. Heathrow is a similar existential issue, worth leaving the government for. No less than two Lib Dem cabinet members have seats near the airport.
But Mr Yeo, like most Tory and Labour MPs, represents a safe seat. He seems to have little comprehension on how elections in marginal seats work. The same seems to be true of BAA and their advisers, who probably like to look at national opinion polls and the big picture. Surprisingly few of the community of advisers, lobbyists and polical professionals that inhabit Westminster have a good understanding of the graft needed to win real elections; even less have any comprehension of how Lib Dem MPs win and hold their seats. So they make silly mistakes like this.
And what of the the case for expanding Heathrow? This deserves a blog in its own right. The case is stronger that my instinctive distrust of BAA, BA and anything calling itself a "business case", or any group purporting to represent "Business", would normally allow. But that is irrelevant in the rough and tumble of winning marginal votes.