David Cameron was roundly applauded in 2011 when he pledged his support for same-sex marriage.
Addressing his party conference in Manchester, he told activists: "I don't support gay marriage despite being a Conservative. I support gay marriage because I am a Conservative."
It was hoped the move would mark the next phase in the “detoxification” of the Tory brand, following pledges to protect spending on international aid and the NHS.
David Cameron hugs a husky
But seven years after he posed with huskies in Norway to stress his green credentials, the outcry sparked by the Marriage (Same Sex Couples) Bill will leave Cameron in no doubt as to the scale of the task.
Critics have been quick to point to the angry opposition on Tory benches, and speeches from MPs like Edward Leigh and Peter Bone as evidence that the modernisation of the party has stalled.
But the Prime Minister’s supporters say gay marriage is a battle worth fighting.
“It’s right that the party pushes on with it as it’s a step in the right direction for the modernisation of the party,” says Ryan Shorthouse, director of the Conservative modernising pressure group Bright Blue.
“It shows Cameron is still a moderniser and wants to make sure the Conservative Party is representative and reflective of the modern world.”
The Conservative Party stands for spreading opportunity, he believes, and access to the institution of marriage should follow.
“To me it’s baffling, as it is to most modernisers in the Tory Party, that we would want to stop relationships based on love from flourishing,” he adds.
Shorthouse believes more votes will be won than lost by pressing ahead.
But many MPs fear that dividing the party and alienating the core support will damage its prospects at the ballot box.
There are plenty of influential voices calling for a return to core “Tory values” and for the “detoxification” project to be ditched.
This leaves the Prime Minister walking a tightrope, according to PR guru Mark Borkowski.
“It’s a very complex strategy,” he says.
“On the one hand you’ve got to keep the chattering classes happy, and on the other you are fighting a back door battle against the likes of UKIP.”
Whatever the reaction, Borkowski believes the Prime Minister was right to introduce the bill.
“I don’t think it was a mistake, it just underlines the challenges,” he says.