There has been a sense of inevitability building around Mark Oaten's withdrawal from the Liberal Democrat leadership race. Of all of the campaigns, his seemed to have the least support from the very start, with a number of his parliamentary backers having said that they would support anyone in the interests of seeing a proper contest. The increasing desperation to stay in the race, culminating in the leaked e-mails, undermined the sense of authority that any prospective leader needs to convey.

To me, Oaten is something of an enigma. He is clearly ambitious, not a bad thing in a man wanting to lead an organisation forward to success. He has, on occasion, shown a willingness to engage with the party's critics and argue for reform when he felt it necessary. But the downside of his character is that he often appears opportunistic, hoping to endear himself to his audience by telling them what they want to hear.

In the end, he failed to convey a real sense of what his leadership would have been like. Optimism and ambition are one thing, but portraying a vision of the future requires more than that. It requires the ability to tie together the various strands of philosophy, pragmatism and presentation and create a compelling case for action. Oaten seemed to be working from the end backwards, aware - perhaps too aware - of the need for action, but lacking the means to explain the purpose of action. Instead of a grand narrative, he produced fractured elements - tough liberalism, sat alongside a liberal attitude towards smoking, with grand claims about ambitions to form a government but little sense of what that government's achievements would be.

This is not to denigrate Oaten's abilities; when he focusses his mind to a specific task, he does well. As shadow home secretary he exceeded many people's expectations in defending civil liberties and promoting a more rounded view of liberal crime policy. His withdrawal highlights the challenge that his rivals will have to overcome, and underlines the need for a leader with a clear vision and sense of purpose.