There are no undergraduate rankings in the traditional disciplines. All the rankings you will see are based on the quality of graduate programs. That being said, a strong graduate program usually indicates that the department has a strong and large faculty, a deep and broad curriculum and undergraduate courses to choose from, research opportunities for undergraduate students, a healthy flow of funding coming into the department etc…Only keep in mind that there are many excellent departments that don’t rank as high but still offer equally good undergraduate education in those fields.
Harvard, Stanford, Princeton, Michigan, Yale, Cal, Columbia, MIT, Duke Chicago, UCSD, UCLA, UNC-Chapel Hill and WUSTL are considered the best political science departments in the country. Half of them are not located in major cities, and none of them are located within 150 miles of Washington DC.
Other good departments…also located far from DC.
Cornell University
Indiana University-Bloomington
New York University
Northwestern University
Ohio State University
University of Minnesota-Twin Cities
University of Rochester
University of Wisconsin-Madison
None of the DC schools has a top rated Political Science department. They are exceptional in International Relations though. If the OP wishes to study diplomacy, foreign service or international relations, Georgetown, GW and AU are truly exceptional. For those interested in a more traditional Political Science degree, being in Washington DC is not required. As Turner aptly and accurately points out, students at all the top Political Science departments mentioned above can secure valuable internships in DC over summer.
All of the universities listed above also happen to have excellent psychology departments.