The fourth test shot of the MX missile was held the other day, a successful and routine launch that caused little stir. But recent developments suggest that the controversial strategic nuclear weapon remains a likely target for congressional budget cutters.
Money for missile production barely squeaked through Congress last year, with lukewarm supporters tying their votes to the promise of arms control. Superpower efforts at Geneva have languished since then, leading a number of those half-hearted backers to waver. Even conservatives on Capitol Hill say that they may not be averse to cutting in half the administration's request for 40 missiles in the coming fiscal year.
Beyond Washington, the MX is being reignited as an important political issue. All three Democratic presidential candidates oppose the missile. Whoever carries the party flag into November is sure to score the administration for continuing the nuclear arms race.
Common Cause is redoubling its effort against the MX, and the so-called ''citizens lobby'' is expected to be especially active this presidential election year.
Wyoming Gov. Ed Herschler (D), who earlier favored basing the MX in his state , recently joined Nebraska Gov. Bob Kerrey (D) in asking the Reagan administration to delay MX deployment. They cited continuing concerns about environmental impact, federal deficit, and the possibility that an arms control agreement could be reached.
''I think the MX is in danger again,'' said Rep. Jim Courter (R) of New Jersey, a member of the House Armed Services Committee. Representative Courter raises questions about deploying the large, highly accurate 10-warhead missile in existing Minuteman missile silos. Critics say placing such a threatening weapon in vulnerable silos is destabilizing because it increases the likelihood of a preemptive enemy attack.
Last year's narrow margin for the MX in the House of Representatives (just nine votes out of 425 cast) ''wasn't a commitment for the missile,'' says Courter, '' it was a commitment for that year's package with arms control.''
There is also a growing sense, as the young New Jersey Republican says, ''that we have to reexamine entirely the strategic doctrine that we have of 'mutual assured destruction.' ''
The first of 100 ''Peacekeeper'' missiles, as President Reagan named them, are scheduled to be deployed in 1986. A recent congressional investigation reportedly warns that this might come before full testing or silo preparation had been completed.
Those urging cuts in the Pentagon's MX request for the coming year also point to Congressional Budget Office findings on the missile's cost.
The CBO reported that approving 21 missiles this year instead of 40 (in other words, the same number as last year) would save $4.4 billion through 1989, assuming there was eventually some progress on arms control.
Terminating the MX program entirely, CBO analysts found, would save $14 billion.
Such a move also would be consistent with the philosophy underlying the administration's strategic-arms reduction proposal, the CBO suggested, particularly the idea that single-warhead missiles that are small and mobile are more stabilizing than large ICBMs in fixed silos.
In recent weeks, there also has been increasing criticism of the President's ballistic missile defense initiative as outlined a year ago in his controversial ''Star Wars'' speech. In its recent final report, the President's Commission on Strategic Forces (the Scowcroft commission) urged ''extreme caution'' in proceeding with a missile defense system that could undercut the Anti-Ballistic Missile Treaty of 1972.
The MX is seen by many as a new generation in multiwarhead missiles that could be used as part of a first strike. In combination with a defense system designed to render an opponent's warheads ''impotent and obsolete'' it is argued , the MX could be seen as even more threatening and therefore likely to increase superpower confrontation.