What did Plato think about government?
Plato's views on government can be found in the Republic as well as the Laws; however, it is only in the Republic that he considers a range of different regimes.
In book IV, he tells us that the ideal regime, the one of his kallipolis, will feature harmony between the three classes in the state: the ruling philosopher kings, the warrior auxiliaries, and the moneymakers (artisans, merchants). The philosopher kings (and, as we find out in book V, queens), who are lovers of wisdom, will rule, and they will be aided in this by the auxiliaries, who love honor above all else. Finally, the moneymakers will consent willingly to be ruled. This resembles most closely an aristocratic government; recall that in Greek, "aristos" simply meant "excellent." Thus, this is a government where the excellent rule.
In book VIII, Plato talks about degenerate governments. This is very interesting and often overlooked in discussions of Plato's political philosophy. After an aristocracy, the next best government, according to Plato, is a timocracy. This is not a good government, though—it's just better than what follows it. In a timocracy, love of wisdom becomes subordinate to love of honor (time in Greek), and it is the warrior auxiliaries who rule, not the philosophers. After a timocracy comes an oligarchy, where only a few (oligos) rich people rule. This happens because people confuse honor with wealth and begin to value wealth above all else. The oligarchy creates such income inequalities and weakens the state so much that it then catches the "virus" of democracy, which, for Plato, is the second worst government. He argues that this is a state with no structure, no laws, and complete anarchy. A democracy, he argues, leads way to the worst government of all: rule by a single tyrant or dictator.