What were the two things people remembered most about Ed Miliband? He stabbed his brother in the back and he was “a bit weird”.

While Jeremy Corbyn has been assembling his shadow cabinet, the Conservatives have launched a campaign to shape the image of the new Labour leader. David Cameron and his team know if they get in early – when most people outside of Labour members still don’t know very much about Jeremy Corbyn – they can paint an image that, if it sticks, will be difficult to shake off.

Before Jeremy Corbyn had even left the venue in which his victory was announced, Michael Fallon – Defence Secretary and the man who, during the Election campaign, reminded voters of Ed Miliband stabbing his brother in the back – was on the BBC describing Mr Corbyn as a risk to Britain’s national and economic security. The Conservative Twitter account had already tweeted out posters with the same message. Michael Gove repeated the line on the Andrew Marr show and now the Conservatives have produced a video: “Labour: a threat to our national security”.

The tactics are clear. The Conservatives are still very much in General Election mode. Messages of security were effective during the campaign and they’re keen to splash their paint onto the blank canvas as quickly as possible. Message discipline. Repeating the effective line until it becomes a truth. This is all out of Lynton Crosby’s playbook.

A leader does not have long to shape his public image. Despite many efforts to “relaunch” his image, Ed Miliband could never shake the tag of Wallace meets Mr Bean and ultimately it was to be his downfall. Wavering voters could not imagine him as Prime Minister and did not trust him and his party with the economy. That image was set very early on in tenure.

Despite his 32 years as an MP, very few of the public know much about the Labour leader, opening a void into which the Tories are chucking rocks. Our own polling suggests the rocks they are throwing have been specifically chosen, with even Labour voters potentially receptive to the messages. Where a hypothetical Prime Minister Corbyn plays worst is the impact he would on Britain’s standing on the world stage. Before his election, more than three times as many people said Britain’s global status would be worse if Mr Corbyn were Prime Minister. Significantly, Labour supporters (not just members but also those currently intending to vote Labour) were more likely to say Britain’s standing in the world would be worse under Prime Minister Corbyn. This was the only area where more Labour voters said it would be “worse” than “better”.

The Conservatives know how to pull the strings. While Mr Corbyn’s first act as leader was to go to a rally for refugees in London, the news will today be carrying pictures of David Cameron at a refugee camp in Lebanon.

Labour’s new team will need to act fast to stop the image from sticking. Not simply by rebutting the attacks, but by building an image of their own. It will need to transcend the loyalists and be relevant and credible to the wider public.

It is not just about what Mr Corbyn stands for – that has its own appeal to certain sections of the electorate. It will also need to be about leadership, strength, trust and competence. He is after all auditioning to be Prime Minister.