Why is it so hard to believe a left-leaning politician might genuinely oppose same-s-x marriage? Julia Gillard is hounded for her “personal view” and now Barack Obama is facing renewed claims of cynical posturing.

A 15-year-old candidate position survey in which Obama, running for the Illinois state senate, pledged his support for same-s-x marriage made headlines again this week.

That support, of course, stands in direct contrast to the position his campaign took when running for president. In 2008, Obama held another view: civil unions, while “separate but equal”, were equal enough for gay and lesbian Americans. Why not full marriage? “God is in the mix,” he explained.

It is a rare sight in politics for a politician to shift from a progressive to a more conservative position, even rarer to do so on a gay rights issue, but until this week few outside the LGBT media had picked up on the story.

That was the case until an embarrassing own goal by White House communications director Dan Pfeiffer, who gave new life to the flip-flop by suggesting in front of a room full of online journalists and bloggers that the document was a “fake”. The White House quickly issued a statement backtracking from Pfeiffer’s claim, but now the story was out and journalists had a new reason to be suspicious of Obama’s stated views.

The day before, Obama’s re-election campaign team fed a story to The New York Times that the president was “evolving” on the marriage equality issue. It was testing the water, a standard practice to see the reaction before deciding what position he would take into the 2012 race.

While polls show Americans are increasingly supportive of marriage equality, those increases are mostly coming from white voters. It is widely assumed Obama has chosen a re-election campaign strategy that relies on mass turnout of Latino and black voters.

If advancing on gay rights presents risks, so does standing still.  The president’s public support for civil unions as a valid alternative to marriage equality has given cover to those who oppose gay rights but, understandably, don’t want to be called a bigot or homophobic.

When NFL Super Bowl star David Tyree declared last week that gay marriage was unnatural and will lead to anarchy, conservative television talk show figure Elizabeth Hasselbeck came to his defence by citing the president’s stance: “… so this is not something that is totally out of the box here”.

It’s those situations that have Democratic strategists reflecting on how much damage the president’s position is doing to enthusiasm in the party’s left wing.

As Crikey hit deadline Obama was attending his first gay-run campaign fundraiser in New York. On the verge of ending the Don’t Ask Don’t Tell policy that banned gays and lesbians from open service in the US military, the president won’t be attending empty handed. But marriage is a big issue in the empire state.

The New York senate is expected to vote on legalising marriage equality today, just hours after the fundraiser. Outside the gala fundraiser protesters chanted “Evolve already”. Inside the $1250 event, supporter were more diplomatic: “Say yes to marriage”.

Progressive blogs have been feeding the notion for the entire length of Obama’s presidency that his opposition to marriage equality was merely a matter of posturing for the sake of expediency. Bill Clinton, much older than Obama, is a supporter, but his even more progressive wife Hillary has been unable to concur as Secretary of State as would contradict government policy.

Fuelling those beliefs has been recent efforts by the Obama administration to declare discrimination against same-s-x couples in federal law as unconstitutional. Also, his support for the repeal of the Defence of Marriage Act that bans any federal recognition of same-s-x couples, married or not.

Like Gillard, there is no evidence that Obama has been lying about his personal ideas of marriage or that his 2008 reversal to a more conservative view was not genuine.

But Obama, more than Gillard, has given himself room to move when his party makes the obvious move that the public has already made.