With little more than 40 days to go until the general election, a dramatic change is already discernible in politics. Obviously, since no vote has yet taken place, it is not an actual shift in the balance of power. Nor is it a seismic movement of any kind in the opinion polls. Nevertheless, the political landscape has altered very significantly.

What has happened is that, under the pressures of an election campaign, the legacy parties have lost their skills, their coherence and their former authority. In short, they have lost the plot. This was never supposed to happen. There was unanimity among the consensus parties and their toadies in the mainstream media that the clowns in this election would be UKIP.

For years now, the Lib/Lab/Con parties have cultivated the notion of UKIP members as quaint and laughable. Tory dinner party conversations now include the statutory clichés about golf club members in blazers (for those who do not recognise this increasingly irrelevant allusion, it is supposed to describe the background and costume of UKIP voters). The Tories might have paused for a moment to recall that golf club members in blazers formerly voted Conservative – one of them was called Denis Thatcher – and to ask themselves if it was really cause for celebration that they no longer do so.

The claim that Nigel Farage is an idiot, a figure of fun who could never be taken seriously, is the central plank of this self-reassuring scenario. No idiot – and no Tory minister, if the distinction is not otiose – could make the speeches he has delivered in the European parliament, speaking truth to power. But such considerations have never been allowed to influence the dismissive attitude of the consensus politicians and media.

In tandem with this fabricated representation of UKIP, the legacy parties and mainstream media have long been playing a game whereby they attempt to eliminate UKIP candidates, whether local, Westminster, or European, almost as soon as they have been selected, by synthetically generating a “row” about some politically incorrect remark they made, probably around the time when Lloyd George was in government, which allegedly disqualifies them from public office.

It need hardly be said that such nit-picking, precious and self-interested witch-hunts massively alienate the voters, who would prefer to see their real concerns addressed. In recent weeks, however, the legacy parties’ infantile attempts to demonise UKIP have begun to rebound against them, to an extent that threatens to affect the outcome of the election. To the surprise of the media, UKIP has turned the tables on its enemies.

The first major evidence of this was UKIP’s successful discomfiting of the Tories by means of an attack advert. Until now, it was the Tories who attacked UKIP as part of their desperate strategy to win back some of the voters they so gratuitously alienated with their crazed “modernising” agenda. The Conservatives, rattled by the Scottish nationalist leader Alex Salmond’s threat to exclude them from government in a hung parliament by supporting a Labour administration, launched an advertisement showing Ed Miliband in the front pocket of Alex Salmond’s suit.

UKIP mischievously parodied this with an identical advert showing David Cameron in the pocket of Jean Claude Juncker. It was not the wittiest riposte ever made in politics, but it was undoubtedly amusing and it made a damning point about Cameron’s impotence to negotiate any new settlement for Britain within the EU, despite his empty rhetoric. The Tories could not conceal their discomfort at being made a laughing stock in this way by the despised UKIP.

Then came the offensive claim by the Conservative candidate for Portsmouth South that UKIP voters were “racists”. This provoked demands for her to stand down and suddenly the Tories were on the defensive over “inappropriate” remarks. Nobody knows better than Nigel Farage and his supporters how irrelevant and tedious such controversies are, but they were right to give the Tories a dose of their own medicine. Again, Conservative unease was palpable. Corporal Jones was right: they don’t like it up ’em.

Long before the election campaign began, Ed Miliband was in a state of crisis; so was Nick Clegg, faced with the certain prospect of the electoral meltdown of his party. But now Dave, too, is disintegrating as a political force. His disastrous admission that he would not remain in office, in the unlikely event of winning the election, was followed by his car-crash appearance at the conference of Age UK. Heckled by angry pensioners, struggling in patronising tones to control the audience, Cameron’s debacle is being compared to Tony Blair’s slow handclap from the Women’s Institute.

These and similar disasters that have overtaken the legacy parties during the past few weeks have demonstrated their lack of connection with the British public and their loss of even the weasel political skills that once enabled them to impose on that public. They have lost authority; eventually they will also lose power.