Election-year doldrums beset White House

President Reagan forged through the first two years of office with considerable political finesse and vigor. Now, with election politics dominating the stage, the momentum of his administration has visibly slowed.

The White House still counts on the strong economic recovery to pull off a decisive Reagan victory in the November election. The President remains popular with the public. In the opinion of most political observers, the Democrats will face a formidable incumbent.

But academic and diplomatic experts note that the Reagan presidency, like most presidencies at its stage, is basically marking time. It is not taking any major initiatives and it faces a host of frustrations.

''There's always a letdown in the third and fourth years because everyone is postponing everything, not doing anything risky,'' says political scientist James Sundquist of the Brookings Institution. ''Whatever an administration does it accomplishes in the first two years, then there is a setback in the midterm elections, then there is drift.''

''At first there was a tendency to see what a president more to the right than most people could do,'' says presidential scholar Betty Glad of the University of Illinois. ''Now the forces that have proclivity to the center are reasserting themselves. Most polls show, for instance, that most people don't want to be bogged down in Central America. So you see more resistance to aid in Congress.''

Recent weeks have seen a number of administration setbacks. Among them:

* The President's nominee for attorney general is under a cloud. Impending investigation by a special prosecutor of Edwin Meese III's finances has focused media attention on ethical lapses in the administration. This could become a campaign issue.

* Reagan could not get the school prayer amendment through the Senate despite heavy personal involvement. Eighteen Republican senators voted against it.

* The administration has had trouble getting the Congress to provide emergency military aid for El Salvador and funds for the antileftist rebels in Nicaragua. The Senate is expected to pass a military aid appropriation for El Salvador but at two-thirds of the level Reagan sought.

* The President had to abandon his proposed sale of Stinger missiles to Jordan. King Hussein, meanwhile, has strongly criticized the United States for failures of policy in the Middle East.

* The President accepted a reduction in defense and other spending requests as well as modest tax increases in order to reach a deficit-reduction compromise with Senate Republicans. Now the Democrats in the House are moving ahead with their own budget plan.

''We're into a presidential election cycle, and it's more difficult for Congress and the President to get much done,'' says a GOP leadership source who asked not to be quoted by name. ''You don't find the same level of cooperation. It'll be rough sailing from here on.''

Other administrations have faced doldrums in third and fourth years. Franklin D. Roosevelt, for instance, won major social legislation in his first 100 days.

The Reagan administration, too, is reluctant to undertake any bold programs, even on issues of vital importance, political analysts say. Despite his interest in immigration, for instance, the President is not expected to lobby vigorously for a new law this year. This is due in part to uncertainty over Justice Department leadership and also to the fact that many Hispanics, whom the President is wooing, oppose legislation pending in Congress.

''In an election year the administration will not do anything to alienate Hispanics,'' says a spokesman of the Federation for American Immigration Reform, ''but that doesn't mean Reagan wouldn't sign a bill if it were handed to him.''

As for the fiscal 1985 budget, Reagan is leaving that largely to Congress to battle out - also awaiting a second term before tackling the deficit dilemma seriously. ''Reagan just went through the motion on the executive budget,'' comments Mr. Sundquist, noting that no sooner was the budget submitted to Congress than economics adviser Martin S.Feldstein and budget director David A.Stockman repudiated it.

Defenders of the administration say President Reagan is doing as well as can be exected at this juncture. ''He's still steadfast about the principles of his administration,'' says a legislative aide to Sen. Richard G. Lugar (R) of Indiana. ''The slowdown in momentum is explainable in terms of the sticky point of the cycle we're in and the extreme sensitivity of the issues - like arms for an Arab country.''

''Previous administrations also started out strong and then had to take some defeats,'' says another Republican congressional backer. ''Reagan's track record was phenomenal, but now he has to compromise a lot more. That's a normal process.''

Democratic lawmakers credit the President with sometimes skillful congressional maneuver, although they are critical of the end result. ''He's doing everything possible to avoid debate on issues like the deficit which are sensitive in the campaign,'' says Sen. Jeff Bingaman (D) of New Mexico. ''By reaching a compromise with the Republican Senate leadership he has totally sidestepped the normal budget process in the Senate.''

With Congress asserting itself more these days, administration officials feel increasingly stymied, especially in the field of foreign policy. Complaining that administration policy is being ''constantly undermined'' by Congress, Secretary of State George P. Shultz said recently that the war powers resolution had usurped the President's constitutional role as commander in chief of the armed forces.

Testifying before a Senate Appropriations subcommittee, Mr. Shultz suggested that the executive and legislative branches should work out a ''common sense'' solution to the question. Legislators had used that act, passed in 1973 after the US withdrawal from Vietnam, to limit the administration's ability to keep American troops in Lebanon.

Many diplomatic experts view the difficulties in American foreign policy - drift in the Middle East, absence of arms control negotiations, cool relations with the Soviet Union - as due less to congressional stumbling blocks than to shortcomings of foreign policy management in the administration. Bureaucratic dissension and failure to make use of high-level expertise, combined with the distraction of the election, are cited as fundamental causes of the problem.

In recent weeks the White House has made mistakes in its legislative strategy , such as failing to touch base with key lawmakers and, in the case of its El Salvador aid request, trying to bypass normal congressional procedures. Political observers see weaknesses creeping into the White House operation, largely because of the departure of several key aides in recent months and growing campaign pressures.