Governments in deep trouble at the end of July are nearly always in a hole again at the start of September. The fleeting tranquillity of August changes nothing fundamental. Not surprisingly, therefore, cabinet ministers awake each day to the same sort of headlines that greeted them before they departed for their holidays. Above all, there is the same restiveness at the top of the Government that marked the dying days of July. What is Alistair Darling up to? Is David Miliband flexing his muscles with the leadership in mind?

Such questions are the consequence of ministerial actions and not media feverishness. Below the fragile Prime Minister, Darling and Miliband are the most important figures in the Government. What they say and how they choose to project themselves matter. After all they hold the most senior posts in the Cabinet. In the current feverish climate, the significance of the duo exceeds the status of their posts.

What makes them especially interesting is that neither expected to be in such highly charged situations at this particular point in their careers. When Gordon Brown appointed his old friend to the Treasury, the two of them envisaged a period of calm stewardship. Until the very last moment, Brown had contemplated appointing his even closer ally, Ed Balls, as Chancellor, but in the end went for the seemingly more tranquil option of the experienced pragmatist who had a genius for keeping his brief away from the front pages.

Darling and the economy have been on the front pages ever since. Being Brown's successor was always going to be a thorny brief. Events make it thornier. Darling is the Chancellor trapped in an economic downturn much worse than he and Brown had originally anticipated, working with a Prime Minister who is fighting to save his own career. What is more, Darling must know that it has always been the long-term plan of Brown to make Balls his Chancellor.

Suddenly the fair-minded, long-serving minister is fighting for his position and reputation, and is seeking to set the right public tone at a time when house prices fall and other costs soar. This is a gargantuan task. I can understand why in such circumstances he was tempted to give an interview during his holiday on a remote Scottish island.

In a dramatically new situation, Darling does indeed need to become a different public figure. He must find ways of conveying the calm, relaxed wit that he displays in private and the essential decency that motivates him. Chancellors can become popular and authoritative figures even in recessions. In the 1970s, Denis Healey was cheered affectionately when he appeared on television shows, often dressed as Father Christmas. I cannot imagine Darling going that far, but for the first time in his career he must acquire a bigger public personality, rather than appear every now and again to make another bleak statement.

Even so, giving an interview on holiday was an error. No one should give interviews on holiday, especially a Chancellor in the midst of economic gloom, when every word must be carefully weighed. No doubt his motives were multi-layered and thought through, but I am sure that he did not go into the enterprise anticipating headlines about Britain facing the worst economic situation in 60 years, a message in its simplest, least flattering form that has gone around the world. In the casual looseness of his language, Darling became too much of a personality and not enough of a Chancellor.

Miliband is blissfully free from worrying about the economic nightmares that burden Darling. But he too finds himself in the stressful role of being leader in waiting. Some leaders in waiting scheme to be in such a position for most of their lives. Miliband has become one without trying very hard. He is not one of life's instinctive plotters. His background is in ideas and policy. He was speaking the truth when he said last summer, amid pleas for him to stand for the leadership, that he was proud to be a cabinet minister. No doubt he is prouder still to be a youthful Foreign Secretary. Nonetheless, events have conspired to make him the leader in waiting, and he has decided to embrace the role. He is ready for it now.

This places him under enormous pressure. Many leaders in waiting fail to become leaders. They cease to be free to say what they want to say. Instead, every word is interpreted through the prism of the leadership. Not so long ago, Miliband could write articles about his ideas, and they were taken as contributions to the debates about Labour's future. Now few of his words are remembered. Instead, Miliband's actions are what capture the interest, the fact that he has spoken becomes more important than what he has said.

His dilemma is highlighted in an article he wrote at the weekend on Britain's approach to Russia. Having decided to make no reference to Brown in an article about Labour's future in July, Miliband went out of his way to convey that he and the Prime Minister were working together on the international front. This was interpreted in some quarters as the Foreign Secretary mischievously claiming equal status to the Prime Minister. He cannot win, at least not for now.

Miliband needs to convey that he is ready and willing to lead, but must also find space so that he is heard as well as watched. Like Darling he needs quickly to discover the skills of a political titan, but in such a demanding situation he made matters worse for himself by writing his article at the end of July, at a point where people were heading for their holidays and when there was no obvious peg for such an intervention. The article was well written. The timing was misjudged, heightening the stakes every time he opens his mouth, not always to his own advantage.

Darling and Miliband are learning the art of politics at the highest level in the most exposed situations. One is Chancellor in gloomy economic times. The other is seen as a possible Prime Minister. Like most ministers, they were sheltered from big political storms by the Blair/Brown duopoly. For more than a decade, the whirling dramas were dealt with exclusively by a Prime Minister, a Chancellor and their most senior confidants. The stifling dominance meant few others had the chance to cut their teeth as they rose up the ministerial hierarchy. Now they must do so with the public watching intensely. They will make mistakes. In a different way, the same applies to Brown. He is learning to be in the top job without being a Leader of the Opposition, a useful preparation for being Prime Minister.

Labour appears rudderless partly because the complex self-interested political calculations of senior figures are not necessarily the same as those of the Government as a whole. As they calculate, they make naive errors ,while they face a Conservative leadership which has mastered the art of politics ruthlessly in the shelter of opposition.

s.richards@independent.co.uk