For a President who once could wrap Congress neatly around his finger, these are difficult times. The Republican-controlled Senate Budget Committee has cut in half his requested rate of defense growth, GOP senators are lining up against his tax cuts, and the House is poised this week to pass a nuclear freeze that he opposes.
Congress seems to be saying that Mr. Reagan and his military advisers are out of step both with Congress and the public.''It's a reprimand to the people that advise him,'' said Senate Budget Committee chairman Pete V. Domenici (R) of New Mexico last week after he joined in a 17 to 4 vote to give the President 5 percent, instead of the 10 percent defense increase he wanted.
In both parties on Capitol Hill members are saying that while Americans still want a strong defense and support some increase, they are not with Reagan on this issue. ''It's a cumulative change over a year or a year and a half,'' says Sen. Slade Gorton (R) of Washington, a member of the Budget Committee, who maintains that the defense vote reflects the mood of the country.
''People are opposed to anything except a modest increase,'' says an aide to House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts. Of the President's effort to persuade the public, he adds, ''It's not working.''
Moreover, the White House, which has been adept at winning over Congress or else striking a compromise at precisely the right time, misread the mood on Capitol Hill. Defense Secretary Caspar W. Weinberger ruffled both Democrats and Republicans by refusing to say how he could cut his budget.
''It was poorly orchestrated,'' says a Domenici aide. ''If it was done correctly, they could have gotten a higher number. Something could have been worked out.'' But Secretary Weinberger stood firm, even when he saw the 10 percent increase was losing.
As Domenici pointed out last week, the budget is still not finished. The final product could be more acceptable to the President in the defense area, but a big switch now appears unlikely. The House has already approved a defense budget figure estimated as low as 2.3 percent real growth.
While the White House tries to recoup its defense loss, it must prepare for a battle on another front. Tax cuts, an important plank in the Reagan program, are also in trouble.
The Democratic-controlled House has already voted for revenue increases far over the President's requests. And last week five moderate Republican senators called for canceling both the 10 percent income tax cut, scheduled for July 1, and indexation of tax rates to inflation, slated for 1985.
''Nobody is calling for tax cuts, indexing, or 10 percent for defense,'' said Sen. Lowell P. Weicker Jr. of Connecticut, one of the GOP five. ''We do hear about interest rates and jobs . . . over and over again.'' The five, who are enough to sway the Senate if all the Democrats side with them, are aiming to raise revenues so that the federal deficit would fall, and, they hope, so would interest rates.
As the Senate Budget Committee begins working on revenue figures this week, no plan has yet gathered a majority. The struggle over taxes could turn out to be more contentious than the one over defense spending.
The most visible challenge to the President's leadership this week comes when the House again takes up the nuclear freeze resolution, scheduled for Wednesday. The call for a ''mutual, immediate, verifiable'' halt to the nuclear arms race has such widespread support in the nation that it is predicted to win despite White House opposition.
Although seen by many as merely symbolic, the vote would at least be a rebuke to the President's approach to arms control.
Beyond the freeze, the Reagan administration is fighting other battles on foreign relations. On Capitol Hill, both parties are reporting growing nervousness over his Central America policies. A Reagan request for $60 million more for military aid to El Salvador is in trouble in a House panel. And members are voicing concerns over reports of covert aid to guerrillas in Nicaragua, although Congress has yet to take action to stop it.
The President could see at least one victory this week. After a long delay, the Senate is expected to confirm his choice of Kenneth L. Adelman as director of the Arms Control and Disarmament Agency.
Another possible victory could come on the MX missile. The President will announce soon his preferred basing plan for the missile. Once the MX has a ''home'' that is acceptable to Congress, it will be difficult to defeat. The missile has a broad base of support in Congress, including Speaker O'Neill.