The Obama administration has reversed a long-held position that it must defend America’s federal ban on same-sex marriage from challenges in the courts.

The 15-year-old law, signed by former president Clinton denying federal benefits to same-sex, couples is key to several “equal protection” cases making their way towards the Supreme Court from the five states and District of Columbia where those marriages are recognised. While Obama had made repeal of the law one of his campaign promises, he had until today maintained that such laws were constitutional, and that his administration was required to defend them from constitutional challenge.

Attorney-General Eric Holder said in a statement that two current cases had brought the case to the Second Circuit Court of Appeal, which had no established standard on whether to treat sexual orientation discrimination like unlawful discrimination targeting race, sex and people over the age of 40:

“After careful consideration, including a review of my recommendation, the President has concluded that given a number of factors, including a documented history of discrimination, classifications based on s-xual orientation should be subject to a more heightened standard of scrutiny. The President has also concluded that Section 3 of DOMA, as applied to legally married same-sex couples, fails to meet that standard and is therefore unconstitutional.”

The backflip was unexpected. Just two months ago the White House had cited the Defence of Marriage Act as its legal justification for denying death benefits to gay soldiers’ spouses.

President Barack Obama’s Road to Damascus had looked like it would take longer than even the Gillard government. The former law professor has maintained his personal view — that marriage is between a man and a woman — did not affect his legal and policy stance of nondiscrimination, but he appeared unwilling to take active steps to realise that policy.

In an interview with The Advocate, the president said he was wrestling with the fact “marriage traditionally has had a different connotation”, adding he had a lot of very close friends who were married gay or lesbian couples.

That interview, conducted just after the Democrats’ disastrous mid-term election loss, hinted that Obama’s preferred plan of legislative solutions, rather than court intervention, was under strain. He admitted his preference may not be possible. The White House strategy of waiting for congressional consensus on contentious social issues has often angered his liberal support base, who saw quick solutions in the many court challenges to DOMA or the military’s Don’t Ask Don’t Tell gay ban.

The new White House spokesman, Jay Carney, wouldn’t speculate today on the likelihood of the new Republican-controlled Congress playing along with Obama’s plan, or how the Congress would react to its law being declared unconstitutional, not by a court, but by the other branch of government.

Republican Speaker John Boehner ignored the “homosexual agenda” bait and questioned the timing: the administration is less than two weeks away from a total government shutdown unless a budget continuing resolution is passed.

Obama really does have just a little too much on his plate right now, with Egypt and Libya, a budget crisis, and unions in boycott around the country over laws against collective bargaining. But this move allows the White House to prepare for the 2012 election by giving one segment of his base what they want and he won’t even have to pick up the phone to lobby a single senator.

Whether the Supreme Court agrees that sexual orientation is a vulnerable class like race, s-ex or age, however, is an open question.