Caspar W. Weinberger and the Pentagon have jumped the first major hurdle in their effort to claim a fifth win in their string of victories on defense spending.
Despite howls of protest from the rest of the Reagan Cabinet, loud grumblings from the Republican leadership on Capitol Hill, and a steady drop in public favor for the ''rearm America'' effort, the defense secretary has kept the support of the only constituent he has needed thus far to win a $300 billion-plus budget for fiscal year 1986: Ronald Reagan.
Mr. Weinberger has agreed to scale back his spending request somewhat for next year. But he has preserved most of his program, especially the steady increases for the following years. With the President's blessing, he has refused to accept the goal of White House Budget Director David A. Stockman to cut even deeper into Pentagon spending in 1987 and '88.
There will be trims here and readjustments there, but the main thrust of the administration's defense buildup has not changed as the Pentagon budget battle now moves to Capitol Hill. At a Pentagon press conference Tuesday, Weinberger called this ''an extremely satisfying result.''
Of the $8.7 billion reduction in defense outlays for 1986 (which leaves a total Pentagon budget of $278 billion), only $2.5 billion is to come from weapons and operational programs. The rest is accounted for by the 5 percent civilian pay cut all federal workers face, a slightly smaller pay raise for those in uniform, revised inflation estimates, and dropping fuel prices.
This leaves a budget increase of about 6 percent for the Pentagon in 1986 (not counting inflation), which is less than the 1981-85 average boost of about 9 percent, but represents a substantially bigger increase than other federal programs would receive under the administration's federal budget for next year.
The Reagan-Weinberger thinking is: Don't give up any more than you have to just as you're about to start talking with the Russians, especially since the Kremlin just announced a 12 percent increase in its military spending; and don't whet Congress's appetite with major cuts of your own which make it appear that you've padded your request.
This strategy worked during the first term; lawmakers gave Reagan 97.5 percent of the military spending he requested from 1981 through 1984. That ploy could backfire, however. In fact, some say that it already has and that Weinberger could have gotten a bit more than he actually did two years ago if he had been a little more tractable when deliberations began that year.
There are also warnings that the administration's whole deficit-reduction package - which relies on large and politically painful cuts in domestic spending - could fall apart.
''Unless there are some major defense cuts proposed in the budget, the domestic cuts will go absolutely nowhere,'' Rep. Jack Edwards of Alabama (third-ranking Republican on the House Appropriations Committee) told a recent gathering of military and industrial leaders.
However, there are several weeks before the administration's spending plan is submitted to Congress. With high-level US-Soviet arms control talks resuming about the same time, Reagan may have a stronger hand.
''Until we see the whole budget picture, I wouldn't want to speculate on its reception,'' Sen. Richard Lugar (R) of Indiana told reporters yesterday. Like many Republicans, Mr. Lugar (who is taking over as chairman of the Senate Foreign Relations Committee) says it would be a bad tactic to give up on such programs as the MX missile and Strategic Defense Initiative (''star wars'') without getting something in return from Moscow.
Politically, Weinberger is stressing the point that the proposed Pentagon spending for 1986 is less than Congress had approved in its longer-range budget resolution guideline just two months ago. And he is stressing that the Defense Department ''will make every effort'' in coming years to hold spending below current estimates.
But he also points out that military spending is unique in that it must be crafted in response to national-security threats and specifically to Soviet trends. And here, he clearly reflects the thinking of the President.
In an interview in the current issue of the conservative publication Human Events, Mr. Reagan said: ''We are not going to make any cuts in defense spending that are going to drive us backward with regard to what we're trying to do in overcoming the years of neglect in guaranteeing our security.''