Support for repealing the military's ban on gays serving openly has weakened significantly over the past six years, a new poll indicates.

A bare majority -- 51 percent -- of active duty troops surveyed oppose allowing gay men and women to serve in the armed forces, according to a survey carried out for the Military Times.

In 2004, a similar survey found that nearly two-thirds, or 65 percent, opposed repealing the military's "Don't Ask, Don't Tell" policy. The Clinton-era rule has seen more than 11,000 soldiers dismissed from duty over the past 17 years when their sexual orientation became known to their superior officers.

But the survey also found a large amount of concern among troops over "how to effectively implement new policies for sharing close quarters and living facilities with openly gay members," the Military Times reports.

The survey's results come a week after the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, became the highest-ranking US soldier to throw his weight behind the repeal of "Don't Ask, Don't Tell."

His support for a new policy that would allow gays to serve was quickly echoed by Colin Powell, himself a former Joint Chiefs chairman, who served as secretary of state under President George W. Bush.

Amanda Terkel at ThinkProgress notes that a majority of Americans now support ending the anti-gay policy. She also points to a survey showing that troops are getting more comfortable with the idea of serving alongside gay people.

But even as military opposition to gays softens, political opposition to a repeal of "Don't Ask, Don't Tell" appears to be hardening. Last week, Sen. John McCain (R-AZ) became perhaps the highest-profile congressional moderate Republican to come out against the repeal.

After a seemingly angry McCain accused Adm. Mullen of ignoring the will of Congress in his call for a "Don't Ask" repeal, the Arizona senator was criticized by many commentators who pointed out he had previously agreed to follow the guidance of the military leadership on the matter.

MSNBC host Rachel Maddow accused McCain of listening to military leaders only until they disagreed with him.

Yet some progressive lawmakers are pushing ahead, despite the opposition. Sen. Kirsten Gillibrand (D-NY) has announced she plans to add an amendment to a defense spending bill that would bar the military from using its allotted money to enforce "Don't Ask, Don't Tell."

Gillibrand called the policy "a hole in the integrity of the United States military."