Take a look at this great map showing the results of the 2010 repeal of Don’t Ask Don’t Tell in the House and the constituents’ feelings on the issue. The Dish reports:
[O]n average public support in a district for a liberal policy towards gays needs to be well over 50% for a Congressman to vote in favor of that policy. Moreover, when opinion in a District changes, Democrats are much more likely to change their votes than Republican Congressmen. The figure [above] illustrates their findings for the Don’t Ask Don’t Tell issue. There were only small pockets in the country where majorities opposed changing the policy. Votes against it in Congress were much more numerous than we would expect from public opinion.