North Carolina voters are heading to the polls today to vote on a constitutional amendment defining marriage as solely between a man and a woman. A law in North Carolina already bans same-sex marriage, but the constitutional amendment would deepen the ban, prohibiting state recognition of other types of domestic unions, including those between same-sex couples. On Monday, Education Secretary Arne Duncan threw his support behind same-sex marriage one day after Vice President Joe Biden said he is “absolutely comfortable” with same-sex couples receiving the same rights as heterosexual couples. President Obama has endorsed civil unions but stopped short of supporting same-sex marriage.