Barack Obama’s decision to support gay marriage has no doubt been timed with careful attention paid to the US electoral cycle. The American Commander-in-Chief definitely did not factor in the political travails of David Cameron on a small rain-lashed island several thousand miles east of Washington. Had he done so, he might have postponed the announcement by a day or two.
It isn’t the biggest story to come out of yesterday’s Queen’s Speech, but people who were watching carefully for prime ministerial capitulations to the Conservative right found one in the absence of proposals to give gay couples equal rights in marriage.
As I write in my column  this week, this is an issue that has acquired emblematic status in the battle over what kind of a Conservative party Cameron leads. In his speech at last year’s Tory party conference , the Prime Minister made the case for gay marriage robustly:
Yes, it’s about equality, but it’s also about something else: commitment. Conservatives believe in the ties that bind us; that society is stronger when we make vows to each other and support each other. So I don’t support gay marriage despite being a Conservative. I support gay marriage because I’m a Conservative.
The fact that the hall applauded at this point was subsequently held up as evidence of the great strides in “modernisation” that the party had taken under Cameron’s leadership.
But it turns out that the party grass roots are less signed up to this view than Downing Street likes to think. I have heard a number of MPs complain that gay marriage was a “hot button” issue in their constituencies and that it provoked Tory voters to abstain or back Ukip in last week’s local elections. It cost the party council seats, say back benchers. Nonsense, comes the riposte from Downing Street. It’s the economy and weeks of headlines about incompetence that hit the party's poll ratings. The very last thing we should do, say Downing Street aides, is veer off into illiberal reaction.
Both are right up to a point. At a national level it is crazy to think that Cameron’s support for gay marriage makes the difference between a majority in 2015 and another hung parliament. At the same time, at local level, it is plainly a problem when activists are outraged by their leader’s opinions.
The gay marriage issue is currently out for formal consultation, so Downing Street could clearly act on it if it was felt to be important enough. The Lib Dems are ardently in favour and would quite happily probe and provoke Tory prejudice on the subject to remind voters that (as they see it) Nick Clegg leads the modern, caring, tolerant wing of the coalition. For precisely that reason, senior Lib Dems very much doubt that Cameron can change the policy. He wouldn't want to give the Lib Dems such a handy stick with which to beat the Tories. He might, however, want to postpone dealing with it to avoid looking as if he is deliberately antagonising his back bench enemies.
Obama’s move makes that approach that little bit harder. Suddenly, everyone of a socially liberal disposition in Westminster - in all three parties – is fired up and praising the US President’s brave moral stand, pointing out how it casts gay equality as a contemporary civil rights issue and puts Mitt Romney on the wrong side of history, held back by Republican tea party fanaticism etc. That is not necessarily company Cameron wants to be keeping.
Liberal Tories, meanwhile, have been watching the party’s right wing mobilise in recent weeks and are feeling the need for a counter-attack. As I have written before , joining the coalition postponed a difficult debate about what kind of movement the Tories want to be – what is their model of 21st Century Conservatism? The leadership is not seriously in question. Cameron is personally secure for now. But the party’s soul is still up for grabs. There is a feeling that Tory internal culture wars are brewing. Gay marriage could end up being much more of an issue for Cameron than he expected when he made that speech last year.