Pictured is a detail of a Boy Scout uniform worn by Brad Hankins, a campaign director for Scouts for Equality, as he responds questions during a news conference in front of the Boy Scouts of America headquarters in Irving, Texas.

The Boy Scouts of America's national leadership will vote Thursday on whether to allow openly gay Scouts in its ranks, a critical and emotionally charged moment for one of the nation's oldest youth organizations and its millions of members.

About 1,400 voting members of BSA's national council are to cast ballots Thursday on a resolution to end a policy that allows youth Scouts to be excluded based only on sexual orientation. The ban on gay adult leaders would remain in place.

The vote is taking place at a resort in Grapevine, Texas, not far from BSA's headquarters, during the national council's three-day annual meeting. The results are expected to be announced shortly after 5 p.m. CDT Thursday.

Gay-rights supporters and opponents have waged impressive campaigns to win support for their arguments in the months leading up to the vote.

Supporters of allowing gay scouts used a political consulting firm and targeted about 120 local Scouting councils where they thought the most votes could be won. Opponents cited Texas code to obtain the names and addresses of voting members from BSA officials so they could send out mailings, and held rallies across the country last week.

Scouting was established in 1910 and claims 2.6 million youth members, in addition to thousands of leaders and volunteers. Its board of directors includes executives and community leaders, and President Barack Obama is its honorary president.

Obama urged the organization to reverse the ban before a national executive board meeting that took place in February, and two high-profile board members - the CEOs of AT&T and Ernst & Young - said they would work from within to change the policy.

The national executive board decided instead to leave the final decision to a national council vote, and the BSA launched a listening tour of surveys and focus groups. BSA President Wayne Perry called on voters to approve the resolution overturning the ban in an opinion piece for USA Today published online Wednesday.

Findings that BSA published on its website illustrate the difficult balancing act it faces.

It said a majority of "adults in the Scouting community" support the current ban, but a majority of current Boy Scouts and Venture scouts do not, according to the findings. About 48 percent of parents of current Scouts support the policy, down from 57 percent three years ago.

One estimate suggested a policy change could cause as many as 100,000 to 350,000 Scouts to leave. And it could also affect donors - just more than half of local councils reported to BSA that their donors supported the current ban.

Of the more than 100,000 Scouting units in the U.S., 70 percent are chartered by religious institutions. While these sponsors include liberal churches opposed to any ban on gays, some of the largest sponsors are relatively conservative denominations that have previously supported the broad ban - notably the Roman Catholic Church, the Church of Jesus Christ of Latter-day Saints and Southern Baptist churches.

The Church of Jesus Christ of Latter-day Saints announced in April that it supports the new proposal. Leaders of some smaller, conservative denominations have opposed it.

"Ultimately we can't anticipate how people will vote but we do know that the result will not match everyone's personal preference," said Deron Smith, BSA's national spokesman.