Proposition 8 was ruled unconstitutional due to considerations of both due process and equal protection by the US District Court for the Northern District of California. The lies and deception that worked so well against average citizens completely failed in court, where Proposition 8 proponents were expected to give actual arguments. Since they have no substantive arguments, they were utterly defeated in every way. They were reduced to responding "I don't know" when asked how they justify the claim that same-sex marriage adversely impacts opposite-sex marriage, and even their own witness, David Blankenhorn, had no choice but to testify against them during cross examination:
Given the lack of any reasonable argument for Proposition 8, it's no surprise that it was furthermore ruled that Proposition 8 "fails to possess even a rational basis". The judgment has been stayed pending appeal, however, so Proposition 8 remains in force at the moment. The case will likely go to the Supreme Court, but since the supporters of Proposition 8 still won't have any rational arguments, they will almost certainly fail again. It's just a matter of time.