David Cameron now faces the same dilemma as his three unsuccessful predecessors as leader since 1997: how to win support in the centre ground while also enthusing core supporters. And he has the threat of an early general election hanging over him before his party has even unveiled its main policies.

All the time, Gordon Brown is trying to knock him off balance, both with new initiatives (starting this morning with a speech on changing the political culture) and by claiming that Mr Cameron is moving to “the Right”.

The current propaganda battle is the main significance of the resignation of Johan Eliasch. His own views do not really matter. He has not been a central figure. Much more important is how his departure will portrayed. The news is a gift for the Brown camp.

Everything that Mr Cameron now does is seen in the light of past failures: the downgrading or abandonment of a modernising strategy around the middle of a Parliament when the party's poll ratings were sagging in favour of a core vote approach emphasising crime, immigration and Europe. Mr Cameron and close advisers such as Steve Hilton have been determined to avoid such a shift, especially since it did not do the Tories any good at subsequent elections.

This debate has been reignited by Mr Cameron's post-holiday fightback after his lacklustre July with his stronger emphasis on social breakdown and crime, and his comment about immigration being “too high”. There has been much speculation about the influence of Andy Coulson, the new media supremo.

Much, though not all, of this comment is exaggerated, and to talk of a “lurch to the Right”, as the Brown camp does, is a gross oversimplification with little real meaning other than as a slogan. The Tories were always going to talk about crime and social disorder, and it would, as David Davis said yesterday, have been very odd for them to have avoided the topic after the murder of Rhys Jones and other gun crimes. Nonetheless there is a deliberate attempt now to boost Tory poll ratings in the short term in the hope of deterring Mr Brown from calling an early election.

The question is less whether Mr Cameron talks about crime and immigration (where his remarks were ambiguous and vague) than what is said about other issues. The Tories have been talking about the NHS and will this week highlight schools and social housing.

The touchstone issue is the environment, where a review group is expected to advocate a strongly “green” approach, including a cap on airport expansion. Many of these ideas are unpopular with Tory MPs and activists. However, greenery has been one of the main themes of Mr Cameron’s leadership. So he will have maintain a delicate balancing act between those opposed to new taxes on pollution and those wanting new green policies. George Osborne, the Shadow Chancellor, tries in an article in The Times today to do this, disappointing those who want immediate dramatic action to roll back the State and to cut taxes, but pointing to a shift in taxation away from income and savings towards pollution, and the longer-term goal of a low-tax economy by making government more efficient.

Mr Cameron is not a free agent. How far he can press his modernising agenda will be determined by not only his own personal standing but also by poll ratings. Paradoxically, the pressures for a greater emphasis on traditional issues will increase, the softer these ratings are. Staying on the centre ground is never easy for an Opposition leader under pressure.

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