As far as the Conservatives have changed under the leadership of David Cameron, Steve Hilton is the driving force. By a considerable margin he is the most innovative and daring figure at the top of his party. Hilton has the advantage of being a true believer in the themes that have at times seemed to define Cameron's leadership. Elected politicians, from Cameron down, make their moves towards his agenda with varying degrees of enthusiasm and partly for expedient reasons.
More than anyone else in the Conservative Party Hilton has sought to flesh out Cameron's most important soundbite that "there is such a thing as society, but it is not the same as the state". He evangelises about the redistribution of power from the centre, a crusade that includes strong support for elected mayors.
Hilton wrote a draft of Cameron's speech on poverty delivered at the end of last year, in which the Tory leader argued that Labour's statist approach had failed and that Conservatives must address the inequality gap. He is fascinated by modern ways of delivering social justice, arguing in some cases that Facebook can do more to change behaviour than government. He is also a great fan of the "nudge" theory of politics in which government seeks to influence outcomes rather than impose them. Unlike Cameron, Hilton had a long-standing interest in green issues well before the duo rose to the top of their party in 2005.
His seniority is a hopeful sign that Cameron enjoys the influence of a Tory promiscuous in his thinking. Hilton once told Charlie Leadbeater, a founder of Demos, when the think-tank was closely linked to Tony Blair, that he would love to join. He could not do so because he was seeking to be a Tory candidate at the time. Now Demos works closely with the Conservatives, not least because of Hilton's role as Cameron's senior adviser.
Although Hilton believes his version of Conservatism is progressive he is still firmly on the right. He is no supporter of the state as an instrument of progress and is a passionate Eurosceptic. Hilton is adamant that Cameron left the centre-right EPP alliance in Brussels because it was the right move, and not as a pragmatic act to appease Eurosceptics in the Conservative Party.
What Hilton has managed to do brilliantly is take traditional Conservative values and place them in a modern setting. What is less clear is whether he will flourish in government if the Conservatives win. If he does, the Cameron government will be more experimental than most voters have realised so far.