By Laura Smith-Spark
BBC News, Washington
Gay marriage, homosexuality in the military, Aids policy and hate crimes are to be the focus of the latest US presidential debate.
The leading Democratic candidates are taking part in the debate
For the first time, contenders for the White House are taking part in a live televised discussion devoted solely to gay and lesbian issues.
Backed by the Human Rights Campaign (HRC), a leading US gay rights advocacy group, it will be broadcast on gay-orientated cable network Logo and streamed live on the internet.
Although candidates from both parties were invited, only the Democrats responded positively, the HRC says, so a corresponding event will not be staged for their Republican counterparts.
The Los Angeles forum could prove a political minefield in a nation where gay rights issues continue to polarise many people, as witnessed in the 2004 presidential elections.
The decision to hold the debate in California reflects the influence the state has gained by advancing its primary elections - when party members choose which candidate to nominate for the head-to-head race - to 5 February.
So what do the Democrats stand to gain or lose by taking part?
Candidates 'on the spot'
According to law professor Daniel Conkle of Indiana University, Bloomington, the fact the debate is taking place at all reflects a remarkable evolution in attitudes towards homosexuality in the US over the past 25 years.
Nonetheless, the issue of gay marriage remains a "huge political hot potato".
On the one hand, many gay couples see the legalisation of gay marriage as being of great symbolic as well as practical significance, Mr Conkle said.
"On the other hand, there is a deep sense of, if nothing else, tradition-based support for confining marriage as an institution to the conventional heterosexual form."
Mr Conkle predicts that the candidates taking part - all the Democratic field except Senators Joseph Biden and Chris Dodd, who both plead scheduling clashes - could well be seen "squirming" as they are put on the spot.
Only Ohio Representative Dennis Kucinich and former Alaska Senator Mike Gravel, both long-shots, have given their full support to gay marriage.
The other candidates are likely to try to "massage" their positions to keep influential gay supporters on-side during the primary election process, Mr Conkle said, even though major shifts in policy are unlikely.
After all, exit polls for the 2004 presidential election suggested that 4% of voters were gay, and that of those 77% voted for Democrats.
"Once they are selected by their parties, you start to see something of a move towards the centre, with the candidates toning down their more one-sided positions in an attempt to get more votes from the middle or members of the opposite party," Mr Conkle added
Questions posed at last month's CNN/YouTube debate clearly exposed the conflicts that exist within the Democratic field over gay marriage.
John Edwards was pressed over his gay marriage views by a pastor
First, two women from New York asked whether they would be allowed to marry each other under the candidates' presidencies. Mr Dodd and New Mexico Governor Bill Richardson both voiced support for civil unions but shied away from backing gay marriage.
Then, former North Carolina Senator John Edwards was asked by a pastor from that state why he felt he could use his Southern Baptist background to justify his opposition to gay marriage.
Pushed to answer, Mr Edwards said he felt "enormous conflict" on the issue. He was personally opposed to gay marriage, he explained, but as president he would not use that "faith basis" to deny anyone their rights.
All the Republicans oppose gay marriage, although former New York Mayor Rudy Giuliani did support gay rights while in office and famously temporarily lived with a gay couple during his divorce.
Meanwhile, wider political and public argument on the issue of gay rights is far from over.
Only one state, Massachusetts, has so far legalised gay marriage. A handful, including California, Connecticut, New Hampshire, New Jersey, Vermont and Washington state, allow civil unions or domestic partnerships.
Thirteen states passed same-sex marriage bans in 2004, and a further eight took the same step in 2006.
A 2007 Pew Research Center poll showed that 55% of Americans oppose gay marriage but that 37%, a sizeable minority, support it.
Another Pew survey last year found that 54% of Americans favour allowing civil unions, up from 45% in 2003.
However, exit polls after the 2006 mid-term elections showed only a minority of black Americans - who tend to support the Democrats - back same-sex marriage or civil unions.
And a Quinnipiac University survey released this week suggests that being backed by gay rights groups turns more voters off a candidate than it attracts.
The danger is that in trying to stick to the middle ground, the Democrats risk letting down their support base among gay voters.
Hillary Clinton and Barack Obama have already come under fire this year from gay supporters for failing to respond strongly enough when the US military's outgoing top commander Gen Peter Pace described homosexual acts as "immoral".
The US military's "don't ask, don't tell" policy, which allows gay people to serve if they do not declare their sexuality or engage in homosexual acts, remains controversial and is sure to be raised at the debate.
While every Democratic candidate has said he or she would like to overturn it, none of the Republican contenders have said they intend to do likewise.
Brad Luna, a spokesman for Human Rights Campaign, said a recent row over the dismissal of valuable Arabic linguists from the military because they were gay had illustrated how important the issue was to wider US society.
He said the Democratic candidates would also be asked about hate crimes legislation, ending workplace discrimination and "kitchen table" issues to do with taxes and benefits for same-sex couples.
"What we want is to take the time in this forum to not just hear a quick sound bite -'yes, I'm for reform of don't ask, don't tell'," he told the BBC News website.
"We want to dig deeper and ask the candidates how they plan on achieving these advancements, what their policies and vision are for attaining equality in America for the GLBT [gay, lesbian, bisexual and transgender] community," he said.
"It really is a discussion about the foundation of equality in our society."
The debate will be broadcast on cable network Logo at 2100 ET/1800 PT on 9 August and streamed live on the internet at LOGOonline.com.