Topeka ? Some changed their minds after doing more research. Others thought the debate had become too emotional or too political.

For a range of reasons, 10 members of the Kansas House shifted their positions late in the legislative session on amending the Kansas Constitution to ban gay marriage. They voted for a proposed amendment in March, but against a similar measure two months later.

Their collective change of heart cost the amendment the two-thirds House majority that would have put it before Kansas voters in November. Rejection of the measure frustrated proponents, who believed the proposal would have been widely supported by Kansans because it endorsed values they cherish.

Any of the 10 seeking re-election this year will likely be at the center of an intense political debate over the amendment.

“This will be a very unpopular vote in my district,” Rep. Bill Kassebaum, R-Burdick, one of the 10, said in an interview.

Kassebaum said he switched his vote because he sensed that too much emotion — and even hatred — marked the public debate over the amendment. Constitutional changes should be approached soberly, he said.

Rep. Ray Cox, R-Bonner Springs, said his vote in March in favor of the amendment nagged at him. Then, he said, he remembered the Rev. Fred Phelps Sr., whose Westboro Baptist Church in Topeka has received national attention for picketing against homosexuality.

“I had voted to put Fred Phelps and his ‘God Hates Fags’ placard in the constitution,” Cox said, referring to the slogan on many of Phelps’ posters. The image moved Cox to vote against the amendment when it came up again in May.

Now, he said, “I am completely at ease with the situation.”

Proposed constitutional amendments need 84 favorable votes in the House and 27 in the Senate.

The House in March voted 88-36 for the amendment banning gay marriage and barring the state from extending benefits associated with marriage to any other relationships, such as civil unions.

In slightly revised form, the amendment won Senate passage May 1 on a vote of 27-13. Three days later, the House vote on the same measure was 79-46, five fewer than needed to submit it to a statewide vote.

Just one House member — Rep. Valdenia Winn, D-Kansas City — switched from voting against the amendment in March but for it in May. Winn said she concluded that a favorable vote would be consistent with her view that important subjects should be settled by voters.

But most attention was focused on the 10 who changed their minds and voted against the measure in May. The Associated Press interviewed all 10.

Four of them were Republicans: Cox, Kassebaum, Lana Gordon of Topeka and Kevin Yoder of Overland Park. Of that group, Gordon has filed for re-election.

Six were Democrats: Marti Crow, Leavenworth; Ruby Gilbert, Wichita; Harold Lane, Topeka; Judy Loganbill, Wichita; Josh Svaty, Ellsworth; and Roger Toelkes, Topeka. Gilbert, Lane and Svaty have filed for re-election, while Toelkes has announced he won’t run again.

House Speaker Doug Mays suggested it was “political suicide” to vote first in favor a gay marriage ban but later against it.

“How do you explain being on both sides of an issue that most people view as black and white?” said Mays, who supports a constitutional gay marriage ban.

Making the decision to switch was a struggle, said most of those who did so.

Loganbill said she was concerned that the proposed amendment was too broad, while Crow said the language seemed vague — particularly in denying benefits associated with marriage to other relationships.

Others pointed out that Kansas already has a law defining marriage as the union of one man and one woman and declaring all other marriages contrary to public policy and void.

Legislators who want to ban gay marriage argued that inserting those words into the Kansas Constitution would protect the policy from being modified by a court or a future Legislature.

But Toelkes said he continued to research the issue after the March vote and concluded a constitutional amendment was unnecessary. Yoder reached the same conclusion and said the amendment became “a political vehicle” designed to mobilize conservative voters.

Gilbert concurred, saying constituents and fellow legislators led her to take a deeper look after the March vote.

“I don’t see the reason we need it,” she said in a telephone interview Saturday.

Lane decided the amendment was unneeded after he reviewed a 2002 decision by the Kansas Supreme Court declaring that a marriage between a man and someone who had sexual reassignment surgery to become a woman was not valid.

The court said that if the Legislature wanted to change the state’s policy on marriage, “It is free to do so; we are not.”

And Gordon came to worry that going beyond a simple ban on gay marriage would invite a federal lawsuit, giving a federal judge some say over language in the state constitution.

Svaty remains firmly opposed to gay marriage but began wondering in March about the wisdom of adopting the amendment. If it were, he said, Kansas churches might come to believe that their teachings are not legitimate unless they are endorsed by state government.

“Morally, I stand with the people who voted for this,” Svaty said.