In this paper, we present a series of semantic analyses of words in political blogs in the setting of categorization of two opposite political orientations: liberal vs. conservative. We classify nouns, verbs, adjectives and adverbs into semantic categories by using the General Inquirer dictionary. Then distributions of these categories and correlations among them are examined both within and between blogs of the two opposite political leanings. Results show that although words of certain categories tend to appear together while others do not within blogs of a political leaning, the semantic category distribution of words used by left-wing bloggers is very similar to those by right-wing bloggers, suggesting single words alone do not account for major difference between these two major categories of blogs. Lastly, by examining preliminary results of association rule mining of nouns, verbs, adjectives and adverbs in sentences, we posit that the similarity and/or difference between blogs of opposite political orientations can be detected by extracting opinion expressions around collocation of nouns and verbs (together with modifiers).