Communism and socialism can be connected to a single major author—Marx—and assessed as deviations from, and implementations or negations of, Marx. Democracy is not amenable to a similar treatment; the towering, single major author on democracy does not exist.
What democracy is cannot be separated from what democracy should be.
To avoid starting out on the wrong foot we must keep in mind, then, that (a) the democratic ideal does not define the democratic reality and, vice versa, a real democracy is not, and cannot be, the same as an ideal one; and that (b) democracy results from, and is shaped by, the interactions between its ideals and its reality, the pull of an ought and the resistance of an is.