Garvan Walshe was national and international security policy adviser to the Conservative Party until 2008.

If Jeremy Corbyn does indeed win, his campaign will provide a masterclass in political insurgency. Devoid of charisma, disrespected by his colleagues, given a mascot’s place on the ballot, this North London Barry Goldwater looks set to be Labour’s most extreme leader ever.

He calls Hamas and Hezbollah his “friends;” has not denied funding a campaign by holocaust denier Paul Eisen, described a convicted hate preacher as an “honoured citizen” would leave NATO and reopen the coal mines. He has mused about putting the most successful leader of his own party on trial for war crimes, and would allow private sector tenants to force their landlords to sell their houses to them. He divorced his second wife partly because she wanted to send their son to a grammar school. This is only what has come out in the last few months. Think of what the Conservative Research Department will find out, about, say, his sympathy for the IRA, when it has four and half years to investigate.

This isn’t just the temporary insanity that afflicts all parties after election defeat. We are witnessing an act of organised political theft by anti-democratic extremists that were thought to have been expelled from Labour’s bloodstream. How have they done so well? There are four main reasons.

Line Speed

The extreme left know what they believe, and therefore what to say: capitalism has failed; it is a tool of the “neo-liberal one per cent;” it exploits people at home and abroad – and “we are the only people who will tell you the truth”. And they are organised: trade unions have supplied more than £75,000 in grants and loans to his campaign. Their individual campaigners have been efficient and unscrupulous. A Labour friend was called up by a Corbyn canvasser who insisted that anybody other than their man was a “Tory.” A reasonable, em, compliment if applied to Kendall, perhaps – but a preposterous absurdity to Cooper or Burnham.

Puffer Fish

Social media changes everything. Old-style leadership campaigns happened in the Westminster village. Relationships with trusted journalists and commentators mattered. The members were consumers.Now, particularly on the Left, where Twitter is far more popular, they have become the transmission mechanism. Social networks have a tipping point: once something is shared enough, it crosses a threshold and appears far more popular than it really is.

Corbyn’s campaign, reactionary in content, has taken a boost from technology, and sowed panic among his opponents. 1990s-style centralised media management has gone the way of floral ties and over-sized suits: with today’s technology it is essential to create at least the appearance of grassroots support, if genuine popular support is then to be obtained. “Astro-turfing,” as this is known in the trade, is no longer an optional extra.

Echo Chamber

It is easy, if you’re left-wing, to surround yourself with like-minded people and expose yourself only highbrow media that confirms your prejudices: when did you last hear a right-wing comedian on Radio Four (perhaps it was P.J O’Rourke, but he had to be imported from America)?

Left-wing people rarely have to confront anyone making good arguments for, say, banks’ role in the financial system, or the need for defence spending, or that not everyone on benefits might be claiming them entirely legitimately. Insofar as they are aware of these positions at all they hear them as caricatures. Corbyn’s campaign appeals to these prejudices, his opponents’ have to compromise with them.

Absent Courage

Corbyn’s biggest advantage has been his rivals’ failure to argue against the substance of his platform. They may have criticised it for being too left-wing to win support in middle England, but not for being wrong in principle. When Gordon Brown tried to win over Corbyn supporters by arguing that his support for Hamas and Hezbollah would make it harder to reduce world poverty, he did not avail himself of the strongest arguments against those organisations.

Corbyn’s rivals have thus, facing an electorate dominated by idealists, conceded the moral high ground to Corbyn’s team. His fellow-travelling with terrorism and anti-semitism, or with Vladimir Putin’s homophobic government, or his endorsement of Venezuela (where peaceful opposition leaders are imprisoned), has gone largely unremarked, while their attacks on his economic policies have lacked the necessary detail. Perhaps tactically wise, for his rivals are hoping to win Corbyn over, this moral weakness has been a strategic blunder.

Though he will lose a General Election of still in place, Corbyn will not prove an immediate political disaster. Expect him to benefit from a honeymoon as disgruntled labour left-wingers return from the SNP and “red UKIP.” Do not however, expect the honeymoon to last. In the Conservative Party, he will face a tougher and more ruthless opponent.