Only a year ago Barack Obama still didn't dare support gay marriage. There are few political issues in history on which voters have changed their minds so fast. Liberals are winning this argument in country after country. More Americans now support than oppose gay marriage, says the Pew Forum on Religion and Public Life. These shifts have thrilled leftwing activists worldwide. Over coffee in dingy offices everywhere, they are debating what they can learn from this triumph. Gay marriage points a way for the left to win on issues from immigration to the “war on drugs”. The lesson: leftists don't need to adopt rightwing policies a la Tony Blair. Instead they need to steal the right's language.

Ever since the “workers of the world” cheerily marched off to fight each other in 1914, the left has been discovering that many of its most cherished beliefs don't sell. Pacifism, internationalism, civil liberties and anti-racism have rarely gone down well with voters. Some core leftist policies are popular: good public services, and making rich people pay for others. But the right has always had most of the crowd-pleasing lines: disdain for minorities, the desire to rise with just your family, reverence for armed force etcetera.

The gay marriage campaign has worked chiefly because it borrows the right's language of “family values”. Gay marriage itself is a side issue. Very few gay people actually want to marry. In the Netherlands, for instance, the first country to introduce gay marriage in 2001, a survey by Rutgers WPF, a centre of expertise on sexual and reproductive health and rights, suggests that about 500,000 people call themselves gay. Yet from 2001 to 2005, only 3 per cent of them married.