By Mariano Castillo, CNN
CNN) - Republican Sen. Rob Portman's flip-flop approval for same-sex marriage, is just the latest change of heart on the issue by conservatives.
Even Democrats like President Obama - have turned around after opposing it. This change in attitude is just one of many milestones for the movement.
Here are five of the most important turning points in the same-sex marriage debate:
1993: In a landmark case, Hawaii's Supreme Court ruled that the state can't deny same-sex couples the right to marry unless it finds "a compelling reason" to do so. It orders the issue back to the state legislature, which then voted to ban gay marriage. This was one of earliest debates on the issue at the state level, and was a precursor to the legal battles nationwide. Today, domestic partnerships and civil unions for same-sex couples are legal in Hawaii.FULL STORY