By any measure, Michael Bloomberg is a political rarity. The Mayor of New York is a prominent Republican that holds (relatively) classical liberal views on both economic and social issues: supporting laissez-faire economics over dirigisme, abortion rights over body fascism, and gay marriage rights over homophobia. Sadly for libertarians, this is a position that doesn’t fit well into the intellectually-stunted dichotomy of American politics, in which economic individualists are usually social statists, and vice versa.

Bloomberg’s uncomfortable compartmentalising into the US system is reflected in his political affiliation; started life as a Democrat, before switching parties in 2001 for purely political reasons (to avoid a tricky primary race in city in which Democrat candidates are ten-a-penny). On Wednesday, he completed the set, left the Republican Party, and declared himself an independent.

The mayor’s decision was made with only one date in mind: 4 November 2008, the day of the next Presidential election. The Bloomberg camp has denied this, but that’s par for the course, similar to a football club’s board giving its manager a vote of confidence (Barack Obama, anyone?). In American politics, one has to go a long way before “no” means “no”, and Bloomberg is not about to make such a statement.

The reason the two main parties matter so much (despite the notoriously weak whip system) is because American politics is dominated by money, and parties bring in the dollars like no-one else. However, as a self-made multi-billionaire, Bloomberg is also one of few politicians to have successfully financed his own campaign in its entirety. In 2001, he spent $73m on the mayoral election - which works out at $50 per vote cast and at over five times what his Democratic opponent could muster. He repeated the feat in 2005. In short, Bloomberg can afford to run as an independent, so why shouldn’t he?

As the not-so-invisible primaries continue to roll, the Republicans and Democrats will start to swiftboat each other, giving Bloomberg the perfect chance to establish his national credentials and build up his base. It comes as Rudy Giuliani has suffered a series of setbacks, possibly allowing Bloomberg to finally step out of the political shadow of his mayoral predecessor.

Ideologically, independence from the straitjackets of the economically-illiberal Democrats and socially-illiberal Republicans makes sense. Financially, it’s not exactly an advantage, but it’s not a major disadvantage to a man worth $5.5bn. Politically, it’s perfect. Despite the denials of his intention to run, Bloomberg’s declaration of independence is too convenient. In fact, the only thing amiss is the date; Bloomberg could have done far worse than to wait two weeks. When better than to issue his Declaration of Independence, and his intention to become the first independent President since George Washington than on July 4th?