By Clare Murphy
BBC News Online
This was not quite the situation President Bush had wanted to find himself in.
Gay marriage may have "troubled" him, as he recently made clear, but it is thought unlikely that he wanted to be the US president who threw his weight behind a constitutional amendment outlawing such unions outright.
However, recent developments in San Francisco - where the mayor has been liberally distributing same-sex marriage licenses - and in the state of Massachusetts - which plans to do the same as of May - are widely believed to have forced his hand.
Even as recently as his January State of the Union address, Mr Bush had refused to endorse an immediate constitutional ban, to the consternation of conservative campaigners. But they did not, as it transpires, have to wait long.
Mr Bush has, to many observers, carried out a careful balancing act during his term in office; he has been keen to keep both his right-wing base on board without alienating the middle ground.
But that base, which includes many who believe homosexuality to be wrong, have become increasingly frustrated by advances towards gay marriages made in recent years.
In 2000, the north-eastern state of Vermont - under the governorship of former presidential candidate Howard Dean - became the first to offer same-sex couples many of the same rights of marriage through civil unions.
President Bush recently supported the Marriage Protection Week
Then, late last year, the Massachusetts Supreme Court ruled that same-sex couples were legally entitled to marry after seven gay couples challenged the law.
Efforts by some Massachusetts legislators this month to enshrine marriage as the union of a man and woman under state law have stalled as the requisite support has been lacking.
Meanwhile, hundreds of gay couples have been flocking to San Francisco where Mayor Gavin Newsom has decided to defy California state law and allow such weddings.
Even before such developments, conservative groups had said they wanted the issue to be a key feature of the November presidential poll.
"We want this to be an election matter. It is a monumental issue that all politicians should be forced to take a stand on," Glenn Stanton, director of social research at Focus on the Family, had told BBC News Online.
Many Americans, polls show, are wary of gay marriage, and few of the Democrat presidential candidates support same-sex marriage.
Indeed, it was Mr Bush's Democrat predecessor, Bill Clinton, who signed the 1996 Defense of Marriage Act - a law which defined marriage as the union of heterosexuals for federal purposes.
It did not, however, prevent states from passing their own laws. Mr Bush is proposing to go the extra mile.
The move is likely to galvanise his conservative base in an election year, but it remains unclear how America's middle ground - however uncomfortable they are with same-sex marriages - will respond to a constitutional amendment.
However Mike Neubecker, a member of a group for friends and families of homosexuals, was unequivocal.
"When the president was sworn in, he pledged to uphold the constitution. It does not honour the constitution to alter it to your own personal prejudice."
His son was married in San Francisco last week.