You'd never know it from the way they badmouth him at the White House. Still less from the unkind cuts those around him take at the president.

But Treasury Secretary W. Michael Blumenthal, after winning bureaucratic battles galore, has emerged as the chief shaper of the administration's economic policy. Since that policy is so far so good, it is something of a puzzle why the achievement does not find expression in better relations between the secretary and the president.

The tale of Blumenthal's bureaucratic wins might provide material for the Guinness Book of Records. Most recently he won out in getting the administration to scale down and postpone the tax-cut request for this year.

A month ago he had his way in persuading the president to make inflation public enemy No. 1. Earlier he proposed and successfully lobbied, the appointment of G. William Miller, head of Textron, to succeed Arthur Burns as Federal Reserve Board chairman.

Before that the administration adopted his view that tax cuts should be emphasized over reform. In 1977 he was on the winning side of the debate that led the president to withdraw the $50 tax rebate from the 1977 economic-stimulus package.

The only visible policy loss sustained by Blumenthal turned on the rhetoric of the dollar. In a speech to the Japan Society a year ago, Blumenthal spoke incautiously about the need for the yen to rise in value relative to the dollar. He was accused of "passivity" when it came to supporting the dollar, which in turn was said to breed a lack of confidence.

Blumenthal touched up his language but stood by his guns. Since then the dollar has snapped back, and the United States has not been oblged to pour outr billions for its support. At the same time Blumenthal has been able to take the lead in heading off a trade war among the industrialized countries.

It is far too early, of course, to pronounce judgments on the results of the policies so largely shaped by Blumenthal. But nothing very bad has happened to date. Almost alone in the industrialized world, the United States has enjoyed a steep rise in employment and a good gain in economic growth. Measures to bank inflationary fires are now being applied. Blumenthal believes the anti-inflationary emphasis will yield for this year a growth rate below the administration's projection of 4 percent. But he thinks anything above 3.5 percent - though that would mean a slight rise in unemployment - is "not too damaging."

At the very least there is room for a certain sense of solace at the White House and the Treasury. If the administration manages the economy as well between now and the election as it has done to date, the president will be a shoo-in.

But in fact relations between Carter and Blumenthal are not warm. An original source of trouble was the Lance affair, because the comptroller of the currency issued the report that eventually led to the resignation of the president's friend and budget director.

But far more important now is the Blumenthal string of victories. On many issues, the Treasury has had its way at the expense of programs dear to Carter personally and to many of his domestic advisers. The emphasis on tax cuts makes Blumenthal look like less than a true-blue loyalist on stamping out the three-martini lunch. A tough line on inflation means cutbacks in spending on welfare, agriculture, health and other items polugged by the domestic departments and White House aides on social policy and political strategy.

Finally there is an undoubted touchiness on Blumenthal's part. Traditionally the secretary of the treasury has been the bridge between government and big business. Blumenthal aspires mightily to that role - and he has the title deed that goes with a successful career as head of the Bendix Corporation.

But President Carter has picked others to woo the tycoons: first Lance, now Ambassador Robert Strauss, who has been named the anti-inflation czar. Blumenthal smarts at those choices, but without reason.

In fact he is too able, he cares too much about policy, to be a mere emissary to fat cats. His strong points are a keen analytic mind, broad practical knowledge of government and business and a capacity to make the right call on the highly complicated interconnected factors that go into economic policy. That may not be the best, but it should be good enough for anybody - not excluding the secretary of the treasury and the president.