The question, then is: to which, ultimately, is democracy owed? To John Locke or to the Protestant Calvinists and Puritans?
Daniel J. Elazar, in his introduction to his volume Covenant & Commonwealth: From Christian Separation through the Protestant Reformation (The Covenant Tradition in Politics, Volume 2), solves the question nicely. Elazar describes how Judaism originated the covenant concept, and that Christianity and Judaism then split in the Roman era. Protestantism then constituted a second split: the Protestant movement, he says, in departing from Catholicism, returned to the Bible (and thus, in a way, to Judaism), thus renewing the covenantal tradition. Elazar then says:
A century later, at the beginning of the modern epoch, a third separation took place in which the covenant traditions of Judaism and Reformed Protestantism were seized upon by philosophers like Spinoza, Hobbes, and Locke, and secularized as compact theory to provide a new basis for a new secular political order. That movement was to reach its apotheosis in the American Revolution, a century and more later, at the climax of the modern epoch. ... Potentially, the conflict between secular compact theorists and religious covenantalists should have been hardly less than that between Christianity and Judaism. In fact, despite the potential for conflict on the theoretical plane, the two came together so well in the practical political application as to paper over real conflicts until the die was cast one way or another, usually in the secular way. The theorists themselves sought to paper over the conflict, perhaps, as Leo Strauss suggests, for self-protection.
In other words: even though the split between Judaism and Christianity, and that between Protestantism and Catholicism were both quite violent and acrimonious, by contrast, says Elazar, the split between Protestant covenantalism and secular social contract was quite decent, civil, and amiable. The two traditions, the religious and the secular, both go together quite well, and together, they both underpin democracy.
One final comment: Elazar said, "...the covenant traditions of Judaism and Reformed Protestantism were seized upon by philosophers like Spinoza, Hobbes, and Locke...". I repeat: the covenant tradition of Judaism was seized upon by Locke. The implication, of course, is that Judaism and democracy ( = John Locke) agree far more often than not.