From ancient Greek period into late 19th or early part of 2oth century traditionalism in scholarship was maintained.
After early 20th century as said by David Easton changes in values, norms and perspectives in the discipline. A reform in methodology and approach.
Machiavelli (Renaissance political thinker), Hobbes, Locke, etc developed new thinking but were classified under traditional view.
Four bases of Classical PS or four values and approaches.
Historical – historical facts and values, historical decision and method influenced much, comparative study and appraisal of constitutions reliable in historic decision.
Analytical – analysis of political facts and views, comparative and analytical study of political subjects like state, law, sovereignty, rights, justice, etc.
Normative or prescriptive – ideals, what ought to be, guidance, explanation and special study of political ideals, norms and values replaced with timely need
Descriptive or taxonomical – Since 1903 after est. APSA, appraisal of political org., distribution and use of power.