These are from his Principles of Political Economy (1821). Needless to say, he’s not in favour of republics or democracy, and rather likes the aristocracy:

And when we consider how very difficult it is, under any circumstances, to establish a well-constituted republic, and how dreadfully the chances are against its continuance, as the experience of all history shews; it is not too much to say, that no well-grounded hope could be entertained of the permanent prevalence of such a form of government (p. 336).

The immediate spur here is the French Revolution, but who is to protect us from such evils?

It is an historical truth which cannot for a moment be disputed, that the first formation, and subsequent preservation and improvement, of our present constitution, and of the liberties and privileges which have so long distinguished Englishmen, are mainly due to a landed aristocracy. And we are certainly not yet warranted by any experience to conclude that without an aristocracy, which cannot certainly be supported in an effective state but by the law of primogeniture, the constitution and liberties so established can in future be maintained (p. 338).

Without such noble gentlemen, the dangers of despotism and democracy are all too real:

Although it be true that a better distribution of landed property might exist than that which actually prevails in this country at present, and although it be also true, that to make it better, the distribution should be more equal; yet it may by no means be wise to abolish the law of primogeniture, which would likely lead to a subdivision of land greater than would probably be favourable even to the wealth of the country; and greater certainly than would be consistent with those higher interests, which relate to the protection of a people equally from the tyranny of despotic rulers, and the fury of a despotic mob (p. 339).