To Catholic voters, President Reagan offered tuition tax credits. To fiscal conservatives, he held out the elusive hope of a budget balanced by constitutional amendment. Responding to minorities and moderate Republicans, he backed extension of the Voting Rights Act. For the religious right, there was school prayer.

"He's fleshing out his presidency," White House communications director David R. Gergen said last week, giving a single explanation for the diverse actions. "These are things he talked about for a long time. It was time to fulfill some of the promises."

Reagan's various responses to specific constituencies form a meandering mosaic reflecting personal commitment, political calculation and opportunities thrust on him by legislation that has worked its way through Congress with no particular impetus from the administration.

They also reflect the inevitable reemergence of issues that are of intense emotional and practical interest to particular interest groups forced off the administration agenda by its single-minded focus on the budget and tax bills of 1981.

The administration's new emphasis on constituency group politics comes during an interlude between the first round of the budget battle and Reagan's foray into global politics.

Economics remains an overriding issue, but the focus on the budget battle has shifted to Congress. In June, when the president is to visit Europe, attention will shift to foreign affairs and what White House advisers see as the useful symbolism of Reagan meeting with world leaders, posing with Pope John Paul II and riding around Windsor Square with Queen Elizabeth II.

"The trip will let the domestic audience see the president as a world leader operating on the grander stage of Europe," one aide said.

For now, however, Reagan has operated on several small stages, each directed to a particular audience. This is the normal consequence of election-year politics and in part a conscious decision--discussed in depth earlier this year by Reagan advisers at Camp David at a meeting the president did not attend--to meet the needs of special constituent groups promised something by candidate Reagan.

Some of the actions, such as Reagan's support of the voting rights compromise, are highly substantive. His support for the compromise engineered by Sen. Robert J. Dole (R-Kan.) was considered a virtual guarantee of its passage.

Other maneuvers, such as the president's reiteration of support for a so-called "balanced budget amendment" that actually would make it more difficult but not impossible for the government to engage in deficit spending, are almost entirely symbolic.

Even by the administration's most generous estimates, next year's deficit will far exceed $100 billion, and few believe that a balanced budget is a realistic hope, even during a two-term Reagan presidency.

Substantive or symbolic or both, the recent constituent-group exercises are viewed in the White House as ratification of a claim increasingly made by Reagan and his most dedicated supporters. Put most simply, it is the view that Reagan, whatever his other limitations, is a president who means what he says and says what he means.

The flame of promise-keeping burns especially bright with Reaganites who worked for the president when he was governor of California.

His closest aide, deputy chief of staff Michael K. Deaver, has been the most insistent advocate of demonstrations by Reagan that he has sympathy for minority Americans. The president tried to demonstrate that last week by visiting a Prince George's County family that had suffered from racial discrimination and by his support of the voting rights compromise.

Another longtime Reagan adviser, White House counselor Edwin Meese III, on Friday listed some of Reagan's commitments on social issues--among them his opposition to abortion, busing and gun control--and observed that the president was keeping his promises on these issues.

Reagan has sent a letter to "pro-life" groups stressing his support for legislation or an amendment outlawing abortion under most circumstances. He supports a bill that would soften weak gun control laws. His Justice Department last week contended that a controversial antibusing rider is constitutional.

To this list could be added the president's declaration that protections for the handicapped apply to severely retarded children. This reflects a belief frequently expressed by Reagan in California during the debate about permissive abortion legislation, which he signed into law and later regretted.

As with the administration's predecessors, it is sometimes difficult to discern whether the White House is controlling events or responding to them.

The voting rights compromise, for instance, was more or less forced on the White House by progress of the legislation through the Congress, the prominent role taken by administration nemesis Sen. Edward M. Kennedy (D-Mass.) and leadership displayed by Dole, one of the Republican senators most influential with the White House.

Other actions, such as the staged announcement on the April 15 income tax deadline of support for a tuition tax credit bill that is probably going nowhere, appear to be acts of purely political calculation.

What stitches these actions together is that each reflects some variation of the many promises Reagan made in campaigning. They are a message aimed at voters that says, "Reagan is a man of his word."

The very success of such actions on individual issues raises questions about the administration's larger accomplishments. While Reagan was promising support for school prayer and tuition tax credits and all of the rest, he was pledging a reduction in federal deficits and taxes and promising that Social Security benefits would not be reduced.

After all of the constituent group politics are played out and the president has returned from Europe and proposed nuclear arms reductions, his advisers acknowledge that the central political issue of 1982 is likely to be the economy. On that issue, Reagan has of necessity retreated from many of the positions he advocated when he submitted his budget last February.

So, at the White House, the very success of Reagan's political policies during the current interlude raises a new question even though the general mood is upbeat after a long "down" period. Many of those close to Reagan see him as moving forward again after a long period of retreat.

But the campaign theme that the White House has struck in this spring of social-issue politics could be the one that comes back to haunt the president in the fall.

Administration spokesmen, and sometimes Reagan himself, boast that he is a president who remembers his promises and does what is necessary to keep them.

It is a springtime yardstick that Democrats are likely to apply to budget deficits, Social Security and the economy when the election campaign refocuses public attention on broader issues this fall.