David Cameron is not the first liberal Conservative to become leader of his party. Before the war there was Stanley Baldwin, who settled the General Strike on fair terms and formed a coalition with the Labour leader, Ramsay MacDonald. After the war there were three liberal Conservative leaders in a row, Winston Churchill, Anthony Eden and Harold Macmillan, who kept the Conservatives in office for 13 years after 1951. I suppose one could also describe Ted Heath and John Major as liberal Conservatives, though not the same sort of liberal Conservative as David Cameron.

The liberal wing of the Conservative Party also produced two outstanding figures who never became the leader — Rab Butler and Iain Macleod. One can certainly compare David Cameron with Macmillan or Macleod, though his image of youth and energy is closer to Macleod. Those of us who remember the postwar Conservative recovery would regard Macleod’s death in 1970 as a great disaster. He was a genuine progressive, in touch with his times, a fine speaker and a shrewd, tough-minded political tactician. He had the best voice of any modern politician; in his conference speeches he projected his best lines like a lyric tenor on the stage of the Royal Opera House.

Mr Cameron became leader a year ago. His first aim was to change the image of the Conservative Party. I never believed this image was quite as bad as Theresa May thought when she was chairman of the party. Most people did not think of the Conservatives as “nasty”, so much as old, out of date and deeply unimaginative. Some people thought them sleazy.

The public attitude could best be summed up in a phrase used by a leading rugby player about the authorities running his sport — “boring, old farts”.

David Cameron wanted to change this to something more contemporary and attractive, with more women and minorities as candidates, with new ideas about the issues the young most cared about, especially the green issues. He believed that this would attract a new audience, and that the polls would improve.

This campaign has gone through some difficulties. The priority list for candidates was harsh, or unfair, to some able young, white men who did not make the A-list. Indeed, it was doubtful whether Mr Cameron himself would have made the A-list if he had been looking for a seat. However, the new system has achieved a higher proportion of women candidates and of local candidates, though helping locals has not been its purpose.

There have also been moments of avoidable infelicity. It was a pity to snub the CBI. Mr Cameron never said “hug a hoody” and never advocated Polly Toynbee’s policies, but somehow he became associated with ideas that irritated his more traditional supporters. These unforced errors were defended because they attracted headlines and left a liberal impression. Unquestionably there was a price to pay. In Somerset, one can quite easily hear the irritated mutterings of loyal Conservatives, though it must be said that many of the critics can be heard defending the Health Service when they are handing out party leaflets. The traditional Conservatives are keen to win.

The poll I rely on most, because of its methodology and track record, is YouGov. Last week YouGov had a poll that showed what is happening. The key question was about Cameron’s strategy. “Are the Conservatives right to focus more and more on green issues, or should they focus instead on taxation, crime and immigration?” By 55 per cent to 37, Conservative voters opted for “taxation, crime and immigration” as the key issues. But Liberal Democrats were “ green” by 56 per cent to 31. For the Lib Dem Party, Mr Cameron is a dangerously attractive Conservative leader, because he shares some of its basic values.

The truth seems to be that Mr Cameron is winning the sympathy, and some of the votes, of Lib Dems at the expense of a certain Tory irritation. However, most of the loyal Conservatives are more interested in winning elections than they are in their own opinions.

From the start of Mr Cameron’s leadership, I’ve been following the polls, particularly YouGov, not in terms of minor movements, but of the different zones of support. On Friday YouGov gave the Conservatives 37 per cent, Labour 32, and the Lib Dems 16. While the Conservatives are over 35, Labour is under 35 and the Lib Dems are under 20, the next election can be won by the Conservatives. That is the essential baseline at this stage. The next election may not come until May or even June of 2010. By then, the Conservatives need to be in the forties to win outright.

That will require two successful stages of policy development, a framework to be unrolled in the next year and detailed policies before the election campaign. The Labour Party has to elect a new leader, who will have to define his own policies. Another YouGov question gets a negative answer for Labour. In a general election with the parties led by Gordon Brown and Mr Cameron, the Conservatives would be in the lead by 43 per cent to 34. That is a winning margin.

Historically, the country has repeatedly put liberal Conservative leaders into Downing Street. Baldwin, Churchill, Eden, Macmillan, Heath and Major won eight elections in the past 82 years. The reason is simple: a liberal Conservative leader can win liberal votes without losing any comparable number of Conservative votes. He can build his own coalition. Such policies can tip over dangerously, as they did for Baldwin in 1930, for Macmillan in 1963, for Heath in 1974 or for Major after 1992. But everything in politics has a risk. The first year of the Cameron strategy has been a success.