Steve Richards: Whatever happens in Glasgow East, it's not going to be the end of Gordon Brown

A wild political year moves towards a gory climax. All eyes are on the Glasgow East by-election, which takes place at the end of this month. Never before has a contest in a single constituency had such an intoxicating advance billing. Parts of the mighty media and a few MPs predict that it could bring about the fall of a prime minister.

Some even pinpoint the event in which the trigger will be pulled, or at least when a deadly weapon will be seized for future use. In this game of Cluedo, the party's policy forum which gathers in the immediate aftermath of the by-election is the equivalent of the library in which the assassin commits a deadly act with some lead piping.

The anticipation is great. Distinguished political journalists are postponing the start of their holidays in case there is a bloodbath. By contrast, some ministers are leaving for their foreign destinations early, unwilling to be close to a microphone to defend Mr Brown if Labour loses. One or two of them note with relief that they are responsible for policy for England and must spend their waking hours on matters far removed from Glasgow East. They will play no role in the by-election.

In Downing Street the event is being viewed with an understandable nervousness. A close aide to the Prime Minister, inhaling deeply on a cigarette, asked a Labour MP who represents a constituency near the scene of the pivotal contest whether he thought it was possible the party could lose. The reply was appropriately apocalyptic: "Don't even go there ... don't contemplate defeat. It is unthinkable". Many Cabinet ministers are working on the assumption that the unthinkable will happen.

There has never been anything quite like this before. Only in retrospect was the Conservatives' defeat in the Eastbourne by-election in 1990 seen as a significant stepping stone in the fall of Margaret Thatcher a few weeks later. At the time, there was virtually no speculation that she would be out of power later in the same autumn.

The closest parallel I can recall is the build-up to the Darlington by-election in 1983 when there was much talk that if Labour lost, Michael Foot would be removed as leader. While that was an epic event, Mr Foot was not a prime minister at the time – one that had been crowned only a year before in an uncontested election. As it turned out, Labour won in Darlington, and I doubt very much if Labour had lost that Mr Foot would have been removed.

This is where the current breathless excitement – the prospect of an apocalyptic, high summer shoot-out – comes up against some awkward realities. The first is that, as in Darlington in 1983, it is possible that Labour will win the by-election in Glasgow East. I would not be especially surprised if Labour scraped home. Nor would I be taken aback if Labour lost. The build-up points to such an outcome, and Labour loses everything it touches at the moment. Either way, the result will not be a surprise. We will learn nothing new.

So what will happen in the event of a defeat for Labour? After a feverish weekend, everyone will go on holiday. That is what will happen. Exhausted ministers are not going to mount a coup in early August. They are desperate for a break, and for some time to reflect. The weekend's policy forum in the immediate aftermath of the by-election will be the opportunity for much behind-the-scenes gossip about the party's future and that of the leader, but there is already much gossip on these themes every day of the week. If there were no by-election taking place, such gossip would still persist.

As for a media that partly drives these stories, I must report sadly that there is a limit to the sacrifices we political journalists are willing to make on behalf of our readers and viewers. We will head off on holiday too. The Glasgow by-election will trigger a fleeting, dramatic eruption – to be followed by a holiday.

That does not mean Gordon Brown is safe in his position. Inevitably, leaders are vulnerable when opinion-poll ratings are dire, the economy slumps and the media turns away. Significant Labour figures, beyond those who have despised him for years, contemplate a switch.

One former cabinet minister, now in the Lords, tells me he was approached recently to see if he would be part of a delegation on permanent standby, prepared at any moment to ask Mr Brown to stand down. In the view of this former minister, there is no route for Mr Brown that leads to a recovery, but he is convinced that the party could win under another leader. Even so, he turned down the request. He was not going to take part in an act of regicide, and was not at all sure that anyone would be willing to wield the knife. His ambiguity is typical and understandable. The stakes are high, and every option is fraught with risks.

Those who predict or call for a change of leader underestimate the difficulties and also the levers still in the hands of an incumbent prime minister. The fall of Mrs Thatcher was sudden and quick. She had little time to prepare for the assault. In contrast, Mr Brown has plenty of advance warning, reading most days of the week that there might at some point be an attempt to remove him.

Mrs Thatcher's departure was also brought about by a combination of MPs' fears that they would lose their seats and alarm at a senior ministerial level about the direction of policy in relation to Europe and the poll tax. Now Labour MPs are as fearful as their Tory counterparts were in 1990, but the policy excuses for a ministerial act of regicide are less clear. Given that a leadership contest could be long and divisive, it is a huge risk to take, not least when Labour would start looking silly in their desperate insularity, crowning another prime minister without holding a general election.

Of course there could be bigger risks in sticking with Mr Brown, but that is not a calculation to be made at the end of a draining political year on the back of a single by-election result. If I were a Labour MP in a marginal seat, or an ambitious cabinet minister, I would wait to see what happens in the autumn; what the political temperature is like after Mr Brown has reshuffled his cabinet and the party conference season has run its course. I suspect that is what they will do.

The autumn will be Mr Brown's testing time. A Labour win in Glasgow East will make his route to the summer recess a little less stressful. A Labour defeat will reinforce the gloom and the hunger among fretful ministers for a break from it all for a few weeks. Such a defeat will be the trigger for an even more confident swagger from the Scottish Nationalists, which could have profound consequences over time. But the contest will not trigger the fall of Mr Brown.