Half of Americans believe gay and lesbian couples have a constitutional right to marriage.

According to a Washington Post-ABC News poll released Friday, 50 percent of respondents say the U.S. Constitution's Equal Protection clause guarantees gay couples the right to marry. Forty-three percent disagree.

Following last June's Supreme Court ruling striking down the Defense of Marriage Act (DOMA), challenges to restrictive state marriage bans have been filed in all but one state, North Dakota – where a challenge is being planned. Marriage equality advocates have yet to lose a case, with a string of judges citing the Constitution's Equal Protection clause.

In states where gay couples are not allowed to marry, 45 percent say the right is a constitutional right and 48 percent say it is not. In states with marriage equality, 56 percent see it as a right.

The survey also found a majority (56%) of Americans support marriage equality, with 38 percent opposed.