Five Americans who changed Tony Blair

1. Will Marshall. In 1992, the President of the Progressive Policy Institute was visited by two young British Labour politicians. One of them was Gordon Brown, he forgot the name of the other.

But the impact on Blair of Marshall and his colleagues in the Democratic Leadership Council was greater. Brown and Blair were visiting to get tips from Clinton associates. The PPI was one of the most fruitful sources. Their working papers helped new Labour get started on a new policy agenda - with a Centre Right bent.

The identity of thinking became so great that Marshall now says that the balance of intellectual payments has changed and that the Democrats are drawing from new Labour. Blair became a new Southern Democrat.

2. Bill Clinton. The election of Clinton profoundly altered Blair and his associates. Philip Gould, Blair's pollster and one of the biggest influences upon him, spent time working on the campaign and absorbed its lessons.

Clinton changed Blair in three ways. First, the Blairites copied Clinton’s "War Room" and began combating the Tories in every news cycle. Second, Tony Blair learned from Clinton's immensely effective rhetorical style. He too began to feel the pain of the middle class. And finally, Clinton's failings hardened Blair. He reacted against the criticism that Clinton avoided hard choices by becoming harder himself. This trait first showed itself during the Kosovo conflict.

3. Rupert Murdoch. Your estimation of the influence of the proprietor of The Sun and The Times on the Prime Minister depends very much on what you think of Tony Blair. Do you think that his politics are on the Centre Right anyway or do you believe that he moved to the Right simply to win the support of the tabloid press? Perhaps it's a bit more complicated than that. Mr Blair provided his own assessment of the relationship last summer in a speech to a gathering of News Corp executives:

Rupert, it’s great to be back at the News Corp conference after all these years. When I first met you, I wasn’t sure I liked you, but I feared you. Now that my days of fighting elections are over, I don’t actually fear you, but I do like you.

This captures perfectly the way Blair has changed during his period in office - what he may have started out doing through necessity, he ended up doing though conviction.

4. Dick Morris. When Bill Clinton was choosing his holiday destination, he turned to his pollster for advice. He ended up in Wyoming. The obsessive use of focus group polling became part of Tony Blair's working method too.

In his book, Behind the Oval Office, about his work for Clinton, Morris set out his methods for developing policy. Morris suggests neutralising the Right on their strong issues - crime and the economy - leaving them to fight where they are weak - education, the environment and so on. Blair followed Morris's methods and ideas very closely.

In fact, Behind the Oval Office, written as a memoir of Morris’s time advising Clinton, remains one of the best texts on Blair's political methods.

5. George W. Bush. The partnership of Bush and Blair, the linking of their names in the public imagination, is an unlikely one. It happened because of Tony Blair's natural liberal interventionism and his view of the importance of the "special relationship". If George Bush had not chosen to invade Iraq, Tony Blair almost certainly would not have advocated doing so. But once the US President had made up his mind to proceed, the British prime minister was never going to allow the Americans to act alone.

Acting together with George Bush has changed Tony Blair in two ways - it has reinforced his interventionist instincts, making that a more prominent part of his political make-up; and it has made him a harder, more ideological politician. He became less reliant on popularity, less concerned about it. And lucky for him that he did, since at the same time he also became a great deal less popular.