The Democrats and Republicans use www.dems.gov and www.gop.gov for their respective House Caucus websites which creates the appearance of a Governmental endorsement of the current two party system.
The GSA's rules for usage of the .gov domain states "No Political or Campaign Information: The Gov Internet domain is for the operation of government, not the political, political party, or campaign environment. No campaigning can be done using .gov domains. The Gov Internet domain websites may not be directly linked to or refer to websites created or operated by a campaign or any campaign entity or committee. No political sites or party names or acronyms can be used. Separate webites and e-mail on other top-level domains (TLDs), such as .org, will have to be used for political activity."