IN CONGRESS, in the country and even in the administration, Prime Minister Ian Smith of Rhodesia has gotten a respectful hearing for his contention that the United States ought to support the "internal settlement" that he and some of the black nationalist made in March. On the level of propaganda he has some considerable successes. But what else does he have? Specifically, does he see a way to convert his public standing (old plus new) into political coin that will actually sustain the Salisbury regime?

Contemplate the question. Rhodesia/Zimbabwe is at war. The situation of the Smith-led government is not one in which even large increments of acceptance and respectability are of much value, except to morale. If the guerillas keep coming on and the economy keeps shrinking and white emigration keeps going up - all likely - then the regard of Americans expressed at a distance will not matter.

The Congress has given Mr. Smith a hearing. But many legislators, we believe, see that as his due and hesitate to go further. It will take some very strenuous doing for the next Congress to lift sanctions and permit normal trade. Not just administration policy but also law (the Case-Javits amendment) require Salisbury first to negotiate with the guerillas and hold elections - two high hurdles. The administration's critics can make Jimmy Carter pay a certain political price for his Rhodesia policy, but they cannot easily get a handle on his diplomancy. Meanwhile, the war gets worse.

We think Mr.Smith would be taking a calamitous risk by concluding from his American swing that, if the internal people will hang on a bit longer, help from the United States will be on the way. His more thoughtful American symphathizers understand this well. They, as we, fear that Mr. Smith will draw a conclusion that will take Rhodesia down a fatal path.

The alternative for Mr. Smith is to take the new sympathy he has won here and to use it to bolster Salisbury's position in negotiations. Too many outsiders, the particular negotiations that seem to be most promising would be with the branch of the guerillas led by Joshua Nkomo, but that is for the Smith government to determine. What with his American trip and the Zambia border opening and his government's new abolition of racial discrimination, he is in what may be the last half-decent position he may ever be in to try to strike a deal.