For the first time, a majority of Americans participating in a Gallup Poll believe that same-sex marriage should be legal and with the same rights as heterosexual marriages.

Results of Gallup's annual 'Values and Beliefs' poll were released Monday (14 May)  but the survey was conducted May 5-8, before President Barack Obama's historic endorsement of gay marriage.

It showed that 53 percent of those surveyed are now in favor of marriage equality - a nine point increase from a year earlier.

The increase, the largest year-to-year shift to date, was exclusively among political independents and Democrats with the views of the Republicans polled unchanged.

The Values and Beliefs poll has tracked attitudes toward legalizing same-sex marriage each year since 2004.

Gallup had also done polling on the topic in 1996 and 1999. In that first poll 16 years ago, two-thirds of Americans were opposed to legalized same-sex marriage and just 27 percent were in favor.

By 2004, support had risen to 42 percent and had stayed roughly at that level through last year.

Clear majorities of both Democrats and independents now support gay marriage, 69 percent and 59 percent respectively. This is in contrast with a mere 28 percent support among Republicans.

But the support even among non-Republicans decreases as those polled are older. Among those aged 18 to 34, there is roughly 70 percent support. There is only about 39 percent support among those 55 and older.

'The issue does, however, remain highly divisive,' Gallup states. 'While big majorities of Democrats and young people support the idea of legalizing same-sex marriage, fewer than 4 in 10 Republicans and older Americans agree.'