The iron triangle is an attempt to examine the three fundamental underpinnings of any successful political party: leader image, economic competence and party unity. Some political commentators believe that these are the best guide to a party's underlying strength.
MORI's Sir Bob Worcester believes that leader image "accounts for between a quarter and a third of the forces that might cause the swing voter to consider moving from one party to another." David Cameron enjoys strong net satisfaction ratings among voters although approximately 40% are yet to make up their mind. This slowness to judgment may partly reflect Mr Cameron's emphasis on reassuring rather than on enthusing voters. He has avoided strong attacks on Labour and he has junked some of the Tory policies that he believes were vote losers (the patients' passport and lower taxation). Mr Cameron's ratings are more positive than his Tory predecessors but fall significantly short of the satisfaction ratings that Tony Blair enjoyed at a similar stage of his own leadership.
The second corner of the triangle concerns economic competence. Labour still enjoys a advantage on this issue (although it is declining) and you can expect Gordon Brown to urge voters to 'play safe with him' at the next election. George Osborne is attempting to neutralise this danger by promising to put stability before tax cuts. The right hates this promise but it's a key component of Team Cameron's wider attempt to pre-empt any Labour attacks on the Tories as "risky" with the nation's finances or with Britain's public services. I have even heard talk of George Osborne promising to match Labour's spending and tax plans for the first year or two years of a Tory government. Labour think that George Osborne is the weak link in the Tories' top team. The Brownites have nicknamed him 'Boy George' and believe that the Shadow Chancellor's youthful looks disadvantage him against the reassuring presence of Gordon Brown and Alastair Darling.
The third point of the triangle is party unity. Voters do not like divided parties and the Tories now enjoy a significant advantage over Labour on unity (in early May ICM found that 64% of voters thought Labour divided but only 48% thought the same of the Conservatives). This week's Clarke attack on Tony Blair is only the latest symptom of a fractious government - built on the faultline between the egos of Blair and Brown. Many Brownites want to reinforce the Chancellor's centrist credentials by seeing him picking fights with the Labour left (as on Trident). This may offer him some benefits but the Tories will try to use such fights as proof of the divided nature of Labour. The fact that the Conservative Party looks united owes much to the loyal shadow cabinet service of David Davis and Liam Fox but there are sources of trouble ahead...
- Ken Clarke's attack on David Cameron's human rights policy was a warning shot from the Europhile left. The cannons of Clarke, Gummer and Heseltine (all now in key party positions) will be much noisier if and when David Cameron delivers on his EPP pledge.
- Whatever David Cameron does on the EPP he threatens party unity. Caroline Jackson et al will leave the grouping of Tory MEPs when we leave the EPP. Dan Hannan et al will leave if we don't. The Cornerstone Group won't tolerate the breaking of this promise either. While William Hague has been clocking up air miles flying to Prague and Warsaw the protagonists have been digging deeper into their trenches. Mr Cameron should probably have delivered on this pledge more quickly but decided not to risk his honeymoon.
- The closed nature of Mr Cameron's inner circle is another threat to unity. Frontbenchers and the policy groups fear that the leader's circle is not sufficiently open to their views. There may be real trouble if they feel ignored and/or used.