John Rentoul: Faraway bombs leave Brown's hopes in tatters

Prime ministers tend to be defined as much by their foreign policy as by what they achieve at home. Eden – Suez; Wilson – Vietnam; Heath – Europe; Thatcher – Falklands; Blair – Iraq. Hence the importance to Gordon Brown of getting Afghanistan right. Just like Barack Obama, he took over from a leader identified with Iraq, and found himself embroiled in another war, which had started before and which will go on afterwards. In both Britain and the US, a foreign war has become caught up in a domestic political drama.

President Obama faces his first crisis of popularity, forced to plead for his health-care reforms at a joint session of Congress this week, as Rupert Cornwell writes today. Brown is in such a pit of unpopularity that his problem is different. For him, Afghanistan is about much shorter-term politics. The two foreign affairs stories of the late summer, the release of Abdelbaset al-Megrahi and the criticism of Brown's Afghanistan policy by Eric Joyce, the Labour MP and former army officer, feed into a Westminster narrative about the Prime Minister's survival as leader of his party.

The immediate focus was not on the content of Joyce's letter of resignation from the junior, unpaid post of parliamentary private secretary (PPS) to Bob Ainsworth, the Defence Secretary. The first question was: is it part of another plot to try to destabilise the Prime Minister?

In this, Brown is partly the victim of the tactics that brought him into 10 Downing Street. Tony Blair was hustled offstage by the co-ordinated resignations of PPSs and the publication of a critical letter. That was a coup orchestrated by Brown's henchpersons. Brown can hardly complain when people assume that similar tactics are being deployed against him. He can hardly be surprised when it is pointed out that Joyce is a Blairite. So Blairite, in fact, that he voted against another inquiry into the Iraq war. He was only PPS to Ainsworth at all because he had held the same post under John Hutton, the once-implacable modernising ultra who resigned unexpectedly three months ago.

It was inevitable, despite Joyce's claim in his letter that "this seems to me the least disruptive time [to resign]", that it would be assumed he had timed his departure for maximum damaging effect, the day before Brown's big speech on Afghanistan.

The real story is rather different. Of course there will be another attempt from within Labour to dislodge Brown, just before or just after the party's annual conference in Brighton at the end of this month. But, like the resignations of Hazel Blears, Jacqui Smith, John Hutton and even James Purnell in June, it will be disorganised and more about people giving up than about a gritty determination to minimise a Conservative win.

Joyce, bruised by the expenses story, sounds to me like someone who is thoroughly fed up. He's no fan of Brown, and would not mind, I suspect, if his criticisms helped to push the Prime Minister out, but he is not part of an organised conspiracy. If only he were.

In fact, I am sure that he is genuinely upset about Brown's handling of the Afghan mission and of the armed forces generally. But his criticisms go straight back to political style rather than substance. He bemoans the lack of directness about Britain's purpose in Afghanistan; and decries "behind-the-hand attacks" on top military brass by any "Labour figure" – a reference to the briefing against General Sir Richard Dannatt. The plain implication is that these are Brown's fault and can be put right only by a new leader; yet not even Joyce will say it.

It was a sign of Brown's weakness that he felt he had to respond to Joyce's letter, and a mark of the clumsiness of his style that he did so not in the text of his speech on Friday but in the briefing of journalists before and after it. Where Joyce had suggested a timetable for pulling out most of our troops "during our next term in government", No 10 seemed to suggest that this could be done by the end of next year – although Brown in his speech suggested only the possibility of speeding up the training of the Afghan army. Joyce's demand for greater clarity about the mission brought forth only greater confusion.

Equally, it was inevitable that Brown's inept handling of the Megrahi affair would be used by his opponents to underline the Prime Minister's unsuitability for the "speed kills" style of modern communications. How Brown must yearn for the political style of 19th-century America: Abraham Lincoln made no speeches or public statements whatsoever during his election campaign in 1860. The obvious implication, among consenting Labour MPs in private, is that a different leader could save them 50 seats simply by understanding the art of contemporary electioneering.

Thus the Westminster story has been diverted into two strands – Brown's character, and conspiracy theories about deals for oil – that have little to do with the underlying issues. I should have thought that the real story of Megrahi's release is one of the unlovely calculations of the national interest, both in London and in Edinburgh. Despite David Cameron's high punitive tone, I wonder if he, had he been in power, might also have sought to get Megrahi to Libya before the end; and I wonder if he might have been relieved when the Scottish administration took the decision for him. He might have been more adroit than Brown in avoiding blame for the whole thing, but the sequence would probably have been the same.

However the Brown story ends, we must be approaching the final chapter. As with so many prime ministers before him, it is framed by foreign events. In Blair's case, it was the Israeli invasion of the Lebanon that was the trigger for his departure. In Brown's case it is his fumbling policy towards Libya and Afghanistan – two names that he can never have expected to see on his political tombstone – that may mark the end of his political career.