The administration is finally doing something about the trade deficit.

No one could seriously maintain that the trade issue has cooled off. Not when 41 senators stand up one after another to denounce the threat of Canadian lumber imports, as they did the other day. But the atmosphere has changed since last year and in ways that offer hope of sounder American policy in this vital area.

Last spring, I wrote a column about the decision of Sen. Lloyd M. Bentsen (D-Texas), an influential member of the Senate Finance Committee and longtime advocate of liberal trade policies, to lend his prestige to an openly protectionist piece of legislation. Joining Chairman Dan Rostenkowski (D- Ill.) of the House Ways and Means Committee and Chairman Richard Gephardt (D-Mo.) of the House Democratic Caucus, he cosponsored a bill that would slap severe tariffs on Japan and other countries unless they opened their home markets to American goods and reduced their trade surpluses with the United States.

Bentsen was frank to say in an interview then that "I'd forget all these things if we had a president who would make this (trade problem) a major priority for the country." Last week, I talked to Bentsen again and he said, "Thank goodness, we've seen some response by the administration. They have begun to move." Bentsen's bill never came to a vote -- but the message got through.

One man who appreciates -- and can claim some credit for -- the improved climate on the touchy import issues is Clayton K. Yeutter. He took over the tough job as the president's special trade representative (STR) just about the time Bentsen & Co. were expressing their exasperation.

When Yeutter was starting, my colleague at The Washington Post, Hobart Rowen, wrote that he had undertaken "mission impossible." Looking back, Yeutter said in an interview last week, he does not disagree. "Economically, politically, it was very tough. I was amazed at the feeling on Capitol Hill -- among Republicans and Democrats -- that no one in the administration was paying attention to the issue."

That is not a rap on Bill Brock, who had the STR job before Yeutter and was shifted to secretary of labor. Brock is one of the ablest people in the administration and a man with many personal friendships on Capitol Hill from his days in the House and Senate. What Yeutter was indirectly confirming is what everyone knows -- that President Reagan and White House chief of staff Donald T. Regan mistakenly thought they could get through 1985 focusing on taxes and budget and summits, and leave the trade problem for manana.

They learned better. While the administration is more doctrinally committed to "free trade" than many on Capitol Hill, it is also more realistic about the economic and political pressures imports create. Congress recognizes the difference. Next week, Rostenkowski will take Yeutter along on the Ways and Means Committee's "retreat" to discuss the shape of the trade bill that Speaker Thomas P. O'Neill Jr. wants ready for action this spring.

The priority the speaker is giving the trade problem is evidence that it remains a potent and painful political issue. From the potato fields of Maine to the copper mines of Arizona, there are thousands, probably millions, of workers and businessmen who see foreign imports as a threat to their livelihoods.

A bill to restrict imports of textiles and shoes, which Reagan vetoed last year, is being kept alive, in suspended animation, awaiting a politically timed override attempt closer to election day. The milder 1986 trade bill that a number of Senate Republicans and House Democrats are framing -- to strengthen the president's authority in seeking "reciprocity" and to limit his discretion in providing import-hardship relief -- may or may not escape a Reagan veto.

Still, Yeutter is not being Pollyannish when he says the climate has improved -- that "there is still concern and perplexity, but not the hostility and animus there was." The administration is taking a harder stance with other countries in a dozen or more specific trade disputes. And the 30 percent decline in the value of the dollar, relative to other currencies, has improved the American competitive position.

It has not had dramatic, or even visible, effects on trade balances as yet. The 1985 trade deficit was by far the worst in history. But many experts back Yeutter's view that the effects will show up, in some instances, later this year, and dramatically in 1987.

Yeutter said he thinks "some of the numbers will be moving in the right direction by this fall." If true, it would be a real relief to Republicans running for reelection.

His surmise is that imports will begin to slacken first, as more and more foreign manufacturers follow the Japanese car makers in raising prices to reflect the readjusted ratio between the yen and the dollar.

U.S. exports will increase more slowly, Yeutter said, because American farm products will still have to compete in a world market glutted by surplus crops, and many manufacturing and business firms were burned so badly in their export efforts in recent years of inflated dollars that they will be hesitant to go back into overseas markets.

But as the United States becomes more competitive, protectionist fevers should ebb -- and that's a break for everyone.