Three-and-a-half months ago, the Reagan administration pointedly refused to set a date for the beginning of new strategic arms negotiations with the Soviet Union because of the "long and dark shadow" of Poland. Today, repression continues there, but President Reagan is ready for the arms talks to begin.

Reagan's decision to go ahead now is a dramatic indication of the flexible politics of arms control and other aspects of superpower relations, an area in which administrations make up the rules as they go along, often with an eye to domestic politics and public opinion.

Reagan, who was bitterly critical of the Carter administration's strategic arms negotiations and SALT II treaty, declared on the eve of the 1980 election that "as president, I will make immediate preparations for negotiations on a SALT III treaty."

Once in office, though, other aims took a higher priority, including a U.S. military buildup, which Reagan had described as "the one card that's been missing" in previous arms control negotiations.

Reagan and others in his administration also spoke on occasion of "linking" Soviet behavior in trouble spots throughout the world to arms control negotiations. "You can't sit down at a table and just negotiate that [strategic arms] unless you take into account--in consideration at that table--all the other things that are going on. In other words, I believe in linkage," Reagan said Jan. 29, 1981, at his first White House press conference.

President Carter had applied "linkage" of a sort on Jan. 3, 1980, by asking the Senate, shortly after the Soviet invasion of Afghanistan, to put aside further consideration of the SALT II treaty. Carter later described his action as a political necessity rather than as a penalty against the Russians, but the connection was clear enough. Consideration of the treaty was never resumed.

By last fall, when Reagan initiated negotiations with the Soviet Union on medium-range weapons in Europe, the planning within the government was for Secretary of State Alexander M. Haig Jr. and Soviet Foreign Minister Andrei A. Gromyko to set a date for the beginning of new strategic arms negotiations when they met in Geneva this News Analysis News Analysis January, and for the negotiators to get down to work in March or April.

By the time Haig met Gromyko, however, martial law had been declared in Poland Dec. 13 and the administration was holding the Soviets responsible, declaring there would be no "business as usual" while repression continued. Moreover, former secretary of state Henry A. Kissinger in mid-January had strongly attacked the administration for proceeding ineffectively with both anti-Soviet sanctions and high-level U.S.-Soviet talks.

In this situation, Haig cut back his Jan. 26 meeting with Gromyko from two days to one (though the talk lasted nearly eight hours anyway), and Haig declined to set a date for the strategic arms negotiations, saying that this would come "when conditions permit," adding, in response to questions, that "the current situation of Poland casts a long and dark shadow over the full range of East-West relations, including the subject of strategic arms talks."

For his part, Gromyko criticized Haig for being "unprepared to begin negotiations on this paramount problem" of strategic arms. He said the Soviet Union remained ready.

On Feb. 10, about two weeks after the Haig-Gromyko meeting, Baltimore Sun diplomatic correspondent Henry L. Trewhitt quoted senior government sources as saying that strategic arms negotiations should begin by June unless "severe internal violence" in Poland or open Soviet military intervention there made this impossible. The State Department would not confirm the story, saying that "the continuing repression" in Poland, by hampering East-West relations, had seriously affected arms control prospects.

In fact, once the Haig-Gromyko meeting had passed without setting a date, the administration's internal target date for the beginning of U.S.-Soviet negotiations was June. There is no sign that developments in Poland affected that timetable, but the growing anti-nuclear protests in this country, including the movement to freeze nuclear weapons, made the nuclear control negotiations seem more urgent. So did a desire to improve Reagan's international image before the president goes to Europe next month.

In his address at Eureka College in Illinois on Sunday, Reagan proposed new U.S.-Soviet strategic arms negotiations in June. His speech made no reference to "linkage" between Soviet behavior and arms control, but spoke instead of "dialogue" and "new understanding" between the two nations.