On most SE sites, when I click on "Chat" link on the top left StackExchange dropdown menu next to the site name, it takes me to the site's main chatroom.
On Politics.SE, it takes me to general SE chat listing all chatrooms; despite the link being site-specific:
http://chat.stackexchange.com/?host=politics.stackexchange.com
The correct link seems to be (based on bluefeet's comment)
http://chat.stackexchange.com/?tab=site&sort=active&host=politics.stackexchange.com