David Cameron is a terrible advert for Oxford PPE. He's long been ignorant of economics - as his prating about the "nation's credit card" and the "global race" attest - but his defeat last night suggests he knows little about politics and history too.

It's a cliche that this was a failure of leadership. I suspect, though, that it was a failure to even see what leadership is. Leadership is the art of getting people to follow you when they don't have to; if they do so because they must, you're not a leader but a boss.

But leadership in this sense is not just about speechmaking and doing the right thing. It's about getting dirty, and using the darker arts of politics.

One such art is timing. If your position is strong, you should act. If it's not, you should wait. Had Cameron waited until the UN inspectors have reported, his case would have been strengthened by reports of the incendiary bomb attack on a school.

But there's another failure. Leadership also means identifying potential oppenents and cajoling them - maybe nicely, maybe not - into supporting you. And at this, Cameron has long been poor. Fraser Nelson says he's "aloof." And only a few months into his permiership one Tory sympathizer wrote:

There is little affection for Cameron on the Tory benches. His regime is chilly, even aloof. MPs who cross him know that they are unlikely to be forgiven. Slowly, the numbers of the disaffected and dispossessed are growing.

Contrast this with two great American leaders - Abe Lincoln and Lyndon Johnson. Their success rested on not so much on them taking the moral high ground - the best that can be said for LBJ's "moral compass" is that it wasn't quite as defective as Nixon's - but on their ability to twist arms, and appeal to low motives.

Their precedents are, I think, relevant. Both men faced parties which were loose and fissiparous, which is the condition of today's Tories. Not only are they intellectually divided - for example on both social and economic liberalism - but they are also socially so; the Cabinet might be full of public school millionaires, but the backbenches aren't. His long failure to close this gap means that Cameron lacked both the ability to convert potential rebels and the trust which was necessary to induce people to follow him on what would have been a speculative venture.

In this sense, there's a tragic aspect to Cameron. He has thought of politics as (by his own lights) a noble venture - as when he pushed through gay marriage and in his desire to stop crimes against humanity. But politics isn't just that. Sometimes, to win a moral crusade you need immoral means. Leadership isn't about being like Martin Luther King, but being like Lyndon Johnson.