AS A CANDID and simple way to buy political support, this week's increase in the support price for milk deserves your attention. There's nothing new or startling about this performance. The Carter administration isn't doing anything that its predecessors haven't done. It's a tradition -- a seedy and unworthy tradition, but one fortified by much history.

Before the end of the day several milk lobbyists will undoubtedly have delivered indignant letters to the editor of this newspaper, arguing that the Agriculture Department has only carried out a routine adjustment required by law. How true. Earlier in the year the Carter administration was in favor of changing the law. The secretary of agriculture, Bob Bergland, strongly advocated it at the beginning of the summer. Then Vice President Mondale, who comes from Minnesota and has a thorough grasp of the dairy situation, had a talk with Mr. Bergland and it appeared that the administration no longer saw any need for change.

Under this law the support price for milk will rise, five weeks before the election, from $12.7 per hundredweight to about $12.73. That's a mere 66 cents. It hardly seems worth much of a fuss, does it? For consumers, that's $1.6 billion a year in higher prices at the checkout counter for milk and milk products.

The lobbyists' letters will suggest that this $1.6 billion is only a modest price to pay for an ensured supply of healthy wholesome milk, butter and cheese. Never mind that there are large surpluses of all those things, and that consumption of both milk and butter -- because of people's anxieties about cholesterol and the rest -- has been falling. Cheese consumption at least is up. (You wouldn't want Americans to be reduced to eating foreign cheese that has been stored in caves and is covered with blue mold, would you?) Beyond the issues of health and sanitation, there is also the purely arithmetical point that Minnesota has 10 electoral votes and Wisconsin has 11.

The debate over the causes of inflation sometimes gets very abstract and remote. It's useful to remember that a lot of inflation is injected directly into the economy by public policies that deliberately increase prices. As long as everyone insists on being compensated fully for past inflation, by tradition and by law, the result will inevitably be further inflation.