If David Cameron succeeds in his efforts to negotiate a better deal from the EU, our new poll shows that he adds 10 points to the power of the remain campaign's argument with swing voters. But that is far from the biggest prize when it comes to winning the referendum.
His real goal is political management - to soothe internal Tory party angst such that he can safely be on the remain side, and none of his potential successors front up for 'leave'.
As things stand, the referendum is on a knife edge, with our poll showing a three-point margin for remain. The vote is heavily conditioned by class and age: middle class people under 55 want to stay by 26 points while working class people over 55 want to leave by 34 points. It is a statistical tie among the older middle class and the younger working class. Among the general population, 13% are on one side or the other but open to changing their mind, and a further 12% don't know either way.
Several things can shift this position, but the biggest potential impact would come if the Tory party lined up solidly behind staying inside the EU. The Tory vote currently breaks 50 to 43 in favour of leaving. However, the pattern in second order elections like referenda is that partisan voters end up voting with their party. With 85% of Tories trusting David Cameron and 81% saying they trust Boris Johnson, if those two shift to be firmly in favour of remaining in the EU, the Tory vote will follow, transforming the race. On the other hand, if the Tory party is seen as ambivalent and divided, voters won't get a clear cue from their party and the potential game changer is missed. With Tory party members strongly anti-EU, the real goal of this negotiation is to allow David Cameron to get decisively into the remain camp without losing his grip on his own party membership.
The role for leadership in the Labour party is much weaker. This is not just because Labour voters are already heavily skewed towards wanting to remain in the EU rather than leave (58 to 31), it also reflects the weakness of the Labour leadership. Jeremy Corbyn is less trusted by Labour voters than Cameron among Tories, yet he is significantly more trusted than Alan Johnson, Gordon Brown or Tony Blair.
When it comes to persuading the public at large, the individual we found who could have the greatest influence on the debate is not a business leader or a politician - it's a journalist. Martin Lewis, the Money Saving Expert, is trusted by 71% of people when he makes arguments about Europe, thirteen points ahead of the next most trusted individual we tested: James Dyson. Stuart Rose is down on 36%. Being a former prime minister seems to help with John Major and Gordon Brown both scoring just below 50% trust. Tony Blair's 32% trust score puts him ahead of Tim Farron.
If the leave campaign fails to get the most influential messengers, it will need to find the most powerful argument. We tested what the two sides say a leave vote means. While 35% agree that a vote to leave is a vote to "take a leap into the unknown, risking a weaker economy, the prospects of future generations and a loss of influence on the world stage"; 47% think it is a is "a vote to make Britain stronger and safer by ending the supremacy of EU law, taking back control, and making sure we can vote for the politicians who make our laws." The leave campaign message is even stronger among swing voters. Add into the mix the heady brew of immigration, the power of anti-elitist sentiment and the fine margin of the remain lead, and it is all to play for.
James Morris is a pollster and communications strategist at Greenberg Quinlan Roser Research