1520s, "science and art of government," from politic (n.) "the political state of a country or government (early 15c., from Old French politique and Medieval Latin politica; see politic (adj.). The plural form probably was modeled on Aristotle's ta politika "affairs of state" (plural), the name of his book on governing and governments, which was in English mid-15c. as (The Book of) Polettiques or Polytykys. Also see -ics.
Politicks is the science of good sense, applied to public affairs, and, as those are forever changing, what is wisdom to-day would be folly and perhaps, ruin to-morrow. Politicks is not a science so properly as a business. It cannot have fixed principles, from which a wise man would never swerve, unless the inconstancy of men's view of interest and the capriciousness of the tempers could be fixed. [Fisher Ames (1758-1808), "British Alliance," in the Boston Repertory, November 1806]
The sense of "political actions or practice" is from 1640s. Meaning "political allegiances or opinions of a person or party" is from 1769.