If the political life is a subset of the active life, which it is, then it is governed by the 4 cardinal virtues. The ruling cardinal virtue is prudence. Without prudence, justice, fortitude and temperance are not possible.
Prudence deals with particulars, including the particular of "which type of regime can best govern this particular group of people at this time." The answer to this question is not limited to "democracy." The idea that a monarchy or an aristocracy is inferior to a democracy on principle is not grounded in reality. Better in practice for some communities? Certainly. Better in practice for many communities that exist today? Maybe. Better always and everywhere on principle? No.
It is an error to turn the prudential judgment of "this type of regime is the one best suited to govern this people at this time" into the universal principle of "this type of regime is superior to all other types of regimes that exist, have existed, or will exist." This error has its roots in the sin of pride. This pride ignores all circumstances and particulars and believes your people and your regime to be the universal form for the just society and the common good. To do this is to replace reality with an illusion. It is an offense against right reason and the truth of things.