Answer: conflict between royal power (embodied in Stuart kings or dynasty) and parliament (certain embodiment of idea of popular sovereignty or limited power of king which was known already in Middle Ages) is directly linked to European reformation. In contrast to countries on the continent English reformation is initiated by the king (Henri VII Tudor: he became a head of national Anglican church), in his personal affairs and political interests. There is also another important point ...specifically English tradition of limiting royal powers that starts already in early 13th century (Magna Carta under king John I, Plantagenet).
Explanation: supporters of parliaments (Whigs) were followers of 1) tradition initiated by Magna Carta, 2) followers of separation from Rome (Roman-Catholicism). Supporters of king (Stuart dynasty) were "Tories" who in a way wanted to return before Henri VIII and before Magna Carta. During civil was the core issue was that the king´s power should not be absolute but limited by the parliament (legislature).
