Democrats in both houses of Congress first attempted to end DADT by amending the Defense Authorization Act.
On May 27, 2010, on a 234–194 vote, the U.S. House of Representatives approved the Murphy amendment to the National Defense Authorization Act for Fiscal Year 2011.
It provided for repeal of the DADT policy and created a process for lifting the policy, including a U.S. Department of Defense study and certification by key officials that the change in policy would not harm military readiness followed by a waiting period of 60 days.
The amended defense bill passed the House on May 28, 2010.
On September 21, 2010, John McCain led a successful filibuster against the debate on the Defense Authorization Act, in which 56 Senators voted to end debate, four short of the 60 votes required.
Some advocates for repeal, including the Palm Center, OutServe, and Knights Out, opposed any attempt to block the passage of NDAA if it failed to include DADT repeal language.
The Human Rights Campaign, the Center for American Progress, Servicemembers United and SLDN refused to concede that possibility.

The American Civil Liberties Union (ACLU) filed a lawsuit, Collins v. United States, against the Department of Defense in November 2010 seeking full compensation for those discharged under the policy.

On November 30, 2010,  the Joint Chiefs of Staff released the "Don't Ask, Don't Tell" Comprehensive Review Working Group (CRWG) report authored by Jeh C. Johnson, General Counsel of the Department of Defense, and Army General Carter F. Ham.
It outlined a path to the implementation of repeal of DADT.
The report indicated that there was a low risk of service disruptions due to repealing the ban, provided time was provided for proper implementation and training.
It included the results of a survey of 115,000 active-duty and reserve service members.
Across all service branches, 30 percent thought that integrating gays into the military would have negative consequences.
In the Marine Corps and combat specialties, the percentage with that negative assessment ranged from 40 to 60 percent.
The CRWG also said that 69 percent of all those surveyed believed they had already worked with a gay or lesbian and of those, 92 percent reported that the impact of that person's presence was positive or neutral.
The same day, in response to the CRWG, 30 professors and scholars, most from military institutions, issued a joint statement saying that the CRWG "echoes more than 20 studies, including studies by military researchers, all of which reach the same conclusion: allowing gays and lesbians to serve openly will not harm the military .... We hope that our collective statement underscores that the debate about the evidence is now officially over...." The Family Research Council's president, Tony Perkins, interpreted the CRWG data differently, writing that it "reveals that 40 percent of Marines and 25 percent of the Army could leave".

Gates encouraged Congress to act quickly to repeal the law so that the military could carefully adjust rather than face a court decision requiring it to lift the policy immediately.
The United States Senate held two days of hearings on December 2 and 3, 2010, to consider the CRWG report.
Defense Secretary Robert Gates, Joint Chiefs Chairman Michael Mullen urged immediate repeal.
The heads of the Marine Corps, Army, and Navy all advised against immediate repeal and expressed varied views on its eventual repeal.
Oliver North, writing in National Review the next week, said that Gates' testimony showed "a deeply misguided commitment to political correctness".
He interpreted the CRWG's data as indicating a high risk that large numbers of resignations would follow the repeal of DADT.
Service members, especially combat troops, he wrote, "deserve better than to be treated like lab rats in Mr. Obama's radical social experiment".

On December 9, 2010, another filibuster prevented debate on the Defense Authorization Act.
In response to that vote, Senators Joe Lieberman and Susan Collins introduced a bill that included the policy-related portions of
Democrats in both houses of Congress first attempted to end DADT by amending the Defense Authorization Act. On May 27, 2010, on a 234–194 vote, the U.S. House of Representatives approved the Murphy amendment to the National Defense Authorization Act for Fiscal Year 2011. It provided for repeal of the DADT policy and created a process for lifting the policy, including a U.S. Department of Defense study and certification by key officials that the change in policy would not harm military readiness followed by a waiting period of 60 days. The amended defense bill passed the House on May 28, 2010. On September 21, 2010, John McCain led a successful filibuster against the debate on the Defense Authorization Act, in which 56 Senators voted to end debate, four short of the 60 votes required. Some advocates for repeal, including the Palm Center, OutServe, and Knights Out, opposed any attempt to block the passage of NDAA if it failed to include DADT repeal language. The Human Rights Campaign, the Center for American Progress, Servicemembers United and SLDN refused to concede that possibility.
The American Civil Liberties Union (ACLU) filed a lawsuit, Collins v. United States, against the Department of Defense in November 2010 seeking full compensation for those discharged under the policy.
On November 30, 2010,  the Joint Chiefs of Staff released the "Don't Ask, Don't Tell" Comprehensive Review Working Group (CRWG) report authored by Jeh C. Johnson, General Counsel of the Department of Defense, and Army General Carter F. Ham. It outlined a path to the implementation of repeal of DADT. The report indicated that there was a low risk of service disruptions due to repealing the ban, provided time was provided for proper implementation and training. It included the results of a survey of 115,000 active-duty and reserve service members. Across all service branches, 30 percent thought that integrating gays into the military would have negative consequences. In the Marine Corps and combat specialties, the percentage with that negative assessment ranged from 40 to 60 percent. The CRWG also said that 69 percent of all those surveyed believed they had already worked with a gay or lesbian and of those, 92 percent reported that the impact of that person's presence was positive or neutral. The same day, in response to the CRWG, 30 professors and scholars, most from military institutions, issued a joint statement saying that the CRWG "echoes more than 20 studies, including studies by military researchers, all of which reach the same conclusion: allowing gays and lesbians to serve openly will not harm the military .... We hope that our collective statement underscores that the debate about the evidence is now officially over...." The Family Research Council's president, Tony Perkins, interpreted the CRWG data differently, writing that it "reveals that 40 percent of Marines and 25 percent of the Army could leave".
Gates encouraged Congress to act quickly to repeal the law so that the military could carefully adjust rather than face a court decision requiring it to lift the policy immediately. The United States Senate held two days of hearings on December 2 and 3, 2010, to consider the CRWG report. Defense Secretary Robert Gates, Joint Chiefs Chairman Michael Mullen urged immediate repeal. The heads of the Marine Corps, Army, and Navy all advised against immediate repeal and expressed varied views on its eventual repeal. Oliver North, writing in National Review the next week, said that Gates' testimony showed "a deeply misguided commitment to political correctness". He interpreted the CRWG's data as indicating a high risk that large numbers of resignations would follow the repeal of DADT. Service members, especially combat troops, he wrote, "deserve better than to be treated like lab rats in Mr. Obama's radical social experiment".
On December 9, 2010, another filibuster prevented debate on the Defense Authorization Act. In response to that vote, Senators Joe Lieberman and Susan Collins introduced a bill that included the policy-related portions of 
Don't ask, don't tell