Gay rights activists received a rebuke from the Deep South to North Dakota as voters in 11 states approved constitutional amendments to ban same-sex marriage in a clean sweep for proponents of traditional one-man, one-woman unions.

“The results just go to show that the citizens … clearly understand the value of natural marriage,” said Christina Rondeau, director of the North Dakota Family Alliance, a group that supported the amendment.

The margin Tuesday in North Dakota was 3-1 in favor – the same as in Georgia and Kentucky as the proposal passed in all 11 states where it was on the ballot. The margin was 6-1 in Mississippi, while the amendment was also approved in Arkansas, Kentucky, Michigan, Montana, Ohio, Oklahoma and Utah.

The issue was put on the ballot in six states through petition drives waged by conservative, church-backed citizens groups. But support of the amendment appeared widespread; in Ohio, it received equal support from men and women, blacks and whites.

Gay-rights activists quickly raised the possibility of court challenges in Georgia, Ohio and Mississippi, although supporters predicted the new laws would hold up.

“Will there be a challenge? Probably, probably,” said Monte Stewart of the pro-amendment “Yes on Three Coalition” in Utah. “Will it succeed? No.”

The most disappointing outcome for gay activists was in Oregon, where supporters of same-sex marriage felt they had the best chance of success.

For gay rights groups, the one-sided results, while disheartening, were optimistically seen as just one strike in an ongoing fight.

The votes will become “a blip in the longer term historic view,” said Karl Olson, executive director of the gay-rights group PRIDE in Montana. “Our constitution isn’t going to be able to sustain this kind of restriction on civil rights.”

The proposed amendments in Mississippi, Montana and Oregon referred only to marriage, specifying that it should be limited to unions of one man and one woman. The measures in Arkansas, Georgia, Kentucky, Michigan, North Dakota, Ohio, Oklahoma and Utah called for a ban on civil unions as well.

“That certainly is disappointing news that many Kentucky voters would think it’s appropriate to write discrimination into our constitution,” said Beth Wilson of the American Civil Liberties Union of Kentucky.

Earlier this year, voters in Missouri and Louisiana came out in favor of gay marriage ban amendments. Louisiana’s amendment was later struck down in state court on the grounds that it improperly dealt with more than one subject by banning not only same-sex marriage but also any legal recognition of common-law relationships, domestic partnerships and civil unions.

Gay-rights activists intend to press marriage-rights lawsuits in states like California and New Jersey, where they believe the high courts might eventually rule in their favor.