The so-called "right to pray" amendment to the Missouri Constitution passed by the kind of margin rarely seen in election referendums.

The measure's supporters said the amendment — called Amendment 2 on the ballot — will protect Missourians' right to pray in public.

"Missourians have affirmed the right to pray in public places and repudiated religious intolerance," said Mike Hoey, executive director of the Missouri Catholic Conference, as early returns showed the measure winning by a sevenfold advantage.

Opponents of the amendment have said Amendment 2's religious protections are already guaranteed by the state Bill of Rights and the U.S. Constitution.

The legislation that led to the amendment had been unsuccessfully sponsored for years by Rep. Mike McGhee, R-Odessa. It passed in the 2011 legislative session — the House on a vote of 126-30 and the Senate on a 34-0 vote.

In an illustration of the measure's popularity, Sen. Claire McCaskill told a reporter in Columbia, Mo., she had voted for it.

In the months leading up to the vote, Amendment 2 prompted unsuccessful lawsuits over its ballot wording, which its critics argued oversimplified the issue to the point of deceit.

The ballot language said the amendment would ensure Missourians' right to express their religious beliefs, schoolchildren's "right to pray and acknowledge God voluntarily in their schools" and require all public schools to display the Bill of Rights.

The ballot did not mention language in the amendment allowing students to refuse to participate in school assignments that violate religious beliefs, or ensuring elected officials the right to pray on government property.

"This was misleading in its presentation and possibly unconstitutional in its application, so now we're headed for the courts," said Karen Aroesty of the Anti-Defamation League of Missouri and Southern Illinois. "We'll let the next branch of the democratic process do its part, and I suspect a case will be on file pretty soon."

Critics have warned the amendment will indeed open the door to taxpayer-funded lawsuits.

"This is going to be a nightmare for school districts, which will end up getting sued by individuals on both sides of church-state debate," said Alex Luchenitser, associate legal director for Americans United for the Separation of Church and State. "This is the most far-out constitutional amendment we've seen in the church-state area."

But the amendment's supporters were thrilled with the large margin of victory Tuesday.

"You don't have to see bringing religion to public square as a threat," Hoey said. "We see it as positive thing, and most Missourians did too."