It’s a Mystery--or Is It?

President Reagan denies political motives for vetoing next year’s $299.6-billion defense spending plan, a declaration that leaves the nation with a real mystery on its hands. The motives can hardly be military, because Congress left out nothing important and put in nothing pernicious, and Reagan got all but 1/20th of 1% of the money that he asked for.

Part of the mystery is how a reduction of that microscopic scale justifies the President’s charge that the budget is a “change away from strength and proven success and back toward weakness and accommodation of the 1970s.”

Defense Secretary Frank C. Carlucci is said to have asked Reagan not to veto the budget before he flew off to Moscow to inspect Soviet military bases and talk strategies for avoiding dangerous encounters. But perhaps the President figured that it was more important to show the Democrats of the House Armed Services Committee who is boss. They had issued a press release bragging that they had taken the “stars out of ‘Star Wars’ ” in the spending bill.

There is some truth to the boast. The President asked for $4.92 billion for research on his vision of a shield to protect America from nuclear weapons, and he got only $4.02 billion--a cut of nearly 20%. But that is not bad for a project that the President alone believes can ever work, and on which all of the useful research could be financed for less than half what Congress authorized.

But even Star Wars took a smaller cut in this budget than it did in the last budget, which the President signed. As for other defense items, Congress gave the Pentagon all but a handfulof the dollars that it requested for its “stealth” bomber project. It approved more M-1 tanks than the White House asked for, gave the Navy money for three new destroyers equipped with Aegis missile-defense systems, and left it up to the next President to decide whether to spend more money on MX missiles that could be moved around on railroads or spend it on smaller mobile missiles, known as Midgetman--a choice so important that time spent pondering it can hardly be said to be wasted.

The only thing we could find in the spending bill that is directly contrary to the President’s wishes is a requirement that the Pentagon dismantle two old Poseidon missile submarines to avoid breaking the limits of a SALT II arms-reduction treaty, signed in 1979 but never ratified by the Senate.

There is no direct evidence that the decision was political, either--especially if you accept that one remark by one Republican could easily be a coincidence.

Sen. Bob Dole (R-Kan.), cheering on the President’s veto, dismissed the defense spending bill as a “Dukakis package.”

Dole is the Republican leader in the Senate and one of two names on Vice President George Bush’s short list as a possible running mate in this year’s presidential campaign against Gov. Michael S. Dukakis. Maybe there is no great mystery after all.