A strong appeal to natural justice? They all help, of course, but are not enough to guarantee success.
Take the recent Dignity in Dying campaign for people who are suffering unbearably to be assisted in ending their lives without risk of prosecution for the assistant. This has enjoyed 82 per cent public support for many years and has a huge list of supporters in the media. Christian groups consider it morally wrong, but that's a religious judgement that they can choose to abide by as believers - the rest of us should be allowed to make our own choices.
And yet the organisation can't seem to win the campaign.
Contrast the work of Dignity in Dying with another rather more successful campaign for social change - the changes in the gambling laws. This is almost the opposite of the assisted dying issue - it has little public or media support and there are few profound issues at stake.
There was certainly a total absence of civil society involvement in this campaign. No angry NGOs filled the newspapers with demands for better access to roulette wheels. No one took direct action and hauled a blackjack table to the top of Big Ben. Not a placard was waved, not a slogan shouted.
And yet the 'campaign' was successful.
So why did one-armed bandits make it when assisted dying failed? There are obviously several case-specific reasons, but there are also general insights to be gained here.
The biggest mistake any campaigner can make is to believe they can win through the quality of their argument. Campaigns are not won because they are 'right', any more than wars are won because of the victor's moral standing. They are won because campaigners can gain access to the power that actually changes things.
In the gambling debate, commercial forces were able to access power very successfully and achieve change despite widespread opposition. In the assisted dying debate the campaign focused on Parliament at first, but soon found out that that's not necessarily where the power lies. There is worse news - its opponents in the churches have even better access to power than Dignity in Dying, and they use it ruthlessly.
So what should Dignity in Dying do? It should take a step back, reconsider the battlefield, do a power analysis, develop a critical pathway for the campaign and try again. The issue is much too important to fail. And it could do worse than tackling the god-botherers head on.