Dangers abroad fully justify the actions ordered by President Carter to deter Soviet adventurism. But so far, Carter lacks the domestic backing he needs to stay the course.

To build a consensus he will have to be a very different president than he has recently been. He will have to stop moral lunges at wrongdoers and begin to lay out a comprehensive strategy. More important still, he will have to come off playing crisis politics on national television.

Dynamic instability at the vortex of world politics constitutes the present danger. The downfall of the shah not only caused government in Iran to pass from friendly to hostile hands. In addition, an imperial presence that played a protecting role across a wide area gave way to a revolutionary theocracy barely able to govern.

Trouble flared in all the border lands of the old imperial domain. From the Middle East to Southwest Asia, existing security arrangements came under pressure.

The monarchies of the Persian Gulf, including Saudi Arabia, all found themselves vulnerable to the anti-Western Islamic fundamentalism distilled in Tehran. Pakistan forfeited a crucial ally for its efforts to balance American and Chinese connections against threats from India and Russia.

The Soviet invasion of Afghanistan, in these conditions, was a major strategic move. Not only did the Russians secure the presence of a satellite regime in Kabul, but they positioned themselves to exploit troubles in Pakistan, Iran and throughout the Persian Gulf.

A strong American response was absolutely required. The more so as the Carter administration had climbed down from confrontation with Moscow over the Russian combat brigade in Cuba and had been warning the Soviets against incursions in Afghanistan since September.

Unfortunately, not many good shots were available. Postponing Senate consideration of the arms control treaty (SALT II) with Russia was minimal. Similarly with drawing down embassy personnel and stopping the sale of high-technology items. The only action sure to make a splash was putting an embargo on sales of grain to Russia.

But Jimmy Carter didn 't have to explain those actions moralistically as a kind of punishment for wrongdoing by the archfiend of "atheism." He could have diagnosed conditions in the area with precision. He could have laid out a program for building strength in the Persian Gulf, and eventually establishing a friendly regime in Iran, and developing a new balance among Russia, India, China and Pakistan. In that context, he could have committed the United States to a permanent naval presence in the Indian Ocean, with support bases in nearby countries.

One reason he didn't is that despite months of dithering on the subject, the administration has still not resolved to seek a permanent naval presence in the area with permanent bases. Another reason is that the Carter administration doesn't think strategically.

Far from finding a new balance in Southeast Asia, the president is publicly dithering about Pakistan in a way that exposes that country to pressure from Russia and the possibility of an attack from the India of Indira Ghandi. By sending Defense Secretary Harold Brown to China with vague talk of "complementary" action, the administration is signing over to Peking an endorsement the Chinese could well use in ways that would embarrass Washington and provoke Moscow.

Whether moral or strategic, the president didn't have to deliver his message on national television. He didn't have to make the announcement of the grain embargo before any arrangements had been made with the farmers, the dealers who own the grain and the longshoremen who move it and other commodities. So why did he feel obliged to go on national television Friday night?

Well, I was in Iowa at the time. Even though I favored the actions announced by the president, it was impossible not to feel that the sudden rush to the screen was totally political, was motivated heavily by a wish to out-flank the Republican debate in Des Moines. So it was not a bit surprising to me to see the leading Republican candidates for president, as well as both Edward Kennedy and Jerry Brown, attack Carter on the grain embargo.

Unless the president is prepared to take himself out of the race, being non-political in the midst of a campaign comes hard. But there is a good test. Anything announced dramatically on national television smacks of domestic politics. So if Carter has finally become serious about national security, if he truly cares to build the consensus required for the difficult times ahead, he will be careful about resort to what, in the present instance, is not, wrongly called the boob tube.