Boris toes the line

David Cameron left the symphony hall in Birmingham’s ICC after Boris Johnson’s speech today beaming – and well he might. The prime minister’s most serious rival for the leadership of the Tory party had just delivered an admirably loyal speech – and while it was entertaining and funny, it did not raise the roof in the way Number 10 must have feared.

The London mayor began his speech in the best way possible if his aim was to damp down speculation about him challenging for the top job, with lavish and lengthy praise for the PM:

If we can win in the middle of a recession and wipe out a 17 point Labour poll lead then I know that David Cameron will win in 2015. [Addressing the PM directly] When the economy has turned around and people are benefiting in jobs and growth from the firm leadership you have shown and the tough decisions you have taken.

And I was pleased to see the other day that you have called me a blond haired mop. A mop. Well if I am a mop then you are a broom. A broom that is cleaning up the mess left by the Labour government and a fantastic job you are doing.

There were very few moments that could be interpreted as a challenge to Cameron. His bald statement that “There will be no third runway at Heathrow” was pretty much the only one.

What Johnson needed to do is downplay expectations of an imminent leadership bid while also reminding delegates why he would do a good job of leading the party. And he did that by striking a very different tone from that of George Osborne the previous day. Where the chancellor warned largely of difficult decisions and tough times ahead, Johnson chose to paint an optimistic vision of sunny uplands to come:

We need to go forward now from the age of excess under Labour, through the age of austerity to a new age of enterprise in which we do what we did in the Olympics and build a world-beating platform for Britain – for British people and businesses to compete and win. And we need to do it now under the Conservatives, and we will, and it begins here.

A cabinet minister remarked to me yesterday that Johnson has a very tricky balancing act on his hands – he needs to remain the heir apparent to Cameron while not overplaying his hand and looking either so disloyal or so indecisive that he offends party members. Gordon Brown managed this trick over an amazing ten years. David Miliband failed in just a few, nearly challenging Gordon Brown twice but looking weak when he failed to do so.

After his speech today, however, Johnson remains on the Brown trajectory rather than the Miliband one.