The MX missile may have gone about as far as it's going. Veteran of years of controversy, the MX appears to have lost most of its congressional support.
Thus, MX deployment -- if it occurs at all -- is likely to stop after a mere 40 missiles are in the ground. And the result could force the Reagan administration to rethink its strategic modernization and arms control positions.
Ironically, the missile's vulnerability has proved its undoing.
When they first began developing the MX more than a decade ago, Pentagon planners wanted 200 of the hulking, 10-warhead missiles. To keep these tempting targets safe from Soviet attack, President Carter proposed shuttling them around vast tracts of Western land in a ``race track'' pattern.
President Reagan criticized this means of deployment. Following the recommendations of a presidential commission, he proposed putting 100 MXs in modified Minuteman silos.
But the Soviets know where those silos are -- and might be tempted to preempt an MX attack by striking them first. It is this vulnerability that lies at the heart of the Senate effort to cap MX deployment at 40 missiles.
``Presidential decisions have deprived the MX of what made it fit into American strategy. That's what's driving the shift away from it on the Hill,'' says Dr. Rodney Jones, director of Nuclear Policy Studies at Georgetown University's Center for Strategic and International Studies (CSIS).
Sen. Sam Nunn (D) of Georgia, author of the amendment to cap MX deployment, said on the Senate floor Wednesday that if Mr. Reagan at some future point could come up with a safer place to put the missiles, the Senate might agree to deploy more than 40.
During the last MX battle two months ago, administration lobbyists argued that Congress had to release funds for 21 MXs because the missile was a necessary ``bargaining chip'' for the Geneva arms talks.
But experts note that after talks started, they quickly focused on possible trade-offs between US space-based defense research and Soviet offensive weapons. The bargaining-chip argument for MX has thus been undercut.
``The question of whether we're in a better bargaining position or not with ongoing MX deployment has been diminished,'' notes Raymond Garthoff, a senior fellow at the Brookings Institution.
The military rationale for the MX, notes Mr. Garthoff, has been its ability to destroy hardened military targets, such as Soviet ICBMs in their silos. This is called counterforce capability.
``But we'll have that capability soon anyway,'' he says, when new Trident II missiles are deployed around 1990.
The USSR, for its part, already has huge missiles of counterforce strength. Many experts consider counterforce missiles to be first-strike weapons -- most useful if launched in a preemptive attack -- and thus destabilizing to the superpower nuclear balance.
So ``if we have too many MXs,'' notes Dr. Jones of CSIS, ``they begin to be exactly what we are angry about on the Soviet side.''
Even as the dance in Congress over the size of the MX program goes on, the missile itself is proceeding smoothly in development. Congress has already authorized purchase of 42 missiles, which include test units and spares. Contracts have been let and construction begun on all 42, say Pentagon officials.
Seven test flights have already occurred at Vandenberg Air Force Base in California. The flights, say Pentagon officials, have gone very well, though there have been some problems with rocket nozzles.
``Taken out of the political context, MX hardware is doing great -- unprecedented reliability, unprecedented accuracy,'' says Capt. Rick Lehner of the Air Force ICBM Modernization Office.
Ten missiles are planned to become operational in December 1986, at an Air Force base near Cheyenne, Wyo. The modification of Minuteman silos to hold the bulky MXs has already begun. Final assembly of production MXs, says Captain Lehner, will take place in silos, not at a factory.