Are President Reagan's favorite issues beginning to lose their hold on American voters?
Is the public becoming more interested in the lagging economy -- high interest rates, unemployment -- than in the issues that brought Mr. Reagan to Washington, namely cutting federal spending and beefing up US defenses?
Democratic leaders -- such as Democratic national chairman Charles Manatt and former chairman Robert Strauss -- say they are convinced this change is taking place and will benefit the Democratic Party, both in congressional votes now and in the fall elections. Only a few months ago they were much less sanguine about Democratic prospects.
Within high administration circles a worry is being voiced more and more that the Reagan thrust to lessen big government is being seriously eroded by a growing public concern about hard times.
Reagan strategists already are reacting to this shift in issues:
* The President, through a policy of what White House spokesmen call ''caution,'' will delay budget battles relating to taxes, defense spending, and social program cuts as long as possible, in the hope that the economy will pick up and give new life to Reagan's anti-big-government issue.
* The President is telling Republicans on Capitol Hill that they will be allowed some ''running room'' in dealing with his extremely large budget deficit. This, administration sources say, is Reagan's way of saying that he is willing to make compromises that recognize growing concern about the economy.
An indication of this moderating viewpoint came Feb. 24 when the administration expressed guarded interest in a sweeping proposal by Senate Budget Committee chairman Pete V. Domenici (R) of New Mexico to slash more than
White House deputy press secretary Peter Roussel called the plan ''a good-faith effort'' that ''we want to take a closer look at.'' It was the first positive response from the administration to an alternative to President Reagan's 1983 budget proposal.
In a speech a day earlier, Senator Domenici warned that the President's budget ''may never get to first base'' in Congress, saying its projected deficits ''threaten to crush any hope of economic recovery.'' The sharp criticism came only hours after GOP congressional leaders personally served notice on Reagan that his budget plan faces ''adjustments'' on Capitol Hill.
* The President is signaling that he will push ahead with his social programs -- anti-busing, anti-abortion, and pro-school-prayer measures, and tax credits for parents with children in private or parochial schools.
Thus, he appears to be putting his emphasis now on promoting social programs that conservatives want, as well as taking a less hard-line approach to further cuts in spending for liberal social programs already in place.
Congressional Democrats are becoming bolder. They're apparently ready to put up strong resistance to President Reagan's efforts to cut longtime social programs. Instead, they say, the public now wants deep cuts in defense spending, and they appear set to champion such reductions.
All this does not mean that the President and Republicans are abandoning Reaganomics and its drive against the concentration of government in Washington. Reagan will stick with that issue. Even the Democrats concede the conservative assault on government spending is far from spent.