THE PRESIDENT'S restrained response to the shooting down of the Korean Air Lines 747 seems to be causing him some political problems on the right. Terry Dolan, head of the National Conservative Political Action Committee, led a demonstration against his policies in Lafayette Square Wednesday, and direct-mail czar Richard Viguerie is denouncing the president for not taking tougher sanctions against the Soviets. How serious is this trouble for the president?

There's no question that Mr. Reagan's actions have disappointed some of the tens of thousands of party workers and campaign contributors who supported him in 1980. They were heartsick about what they considered American reverses during the Carter years, from the SALT II and Panama Canal treaties to Afghanistan and Iran. Now they see Mr. Reagan unwilling to cut off disarmament talks with the "evil empire," as he has called the Soviet Union, and not even willing to impose a grain embargo as President Carter did in 1979.

Will such discontent produce a primary opponent for Mr. Reagan? "A week ago I would have said no," Mr. Viguerie says, "but now I have to hold that open." Reagan strategists regard this as an empty threat: there are no obvious candidates; no public officials have joined Mr. Viguerie's protest. And there's little reason to believe that the Republican core, which has been more faithful to Mr. Reagan than to any other politician in decades, is about to desert. 4 A more serious threat is that the enthusiasm of Mr. Reagan's base may be diminished. If a couple of million 1980 Reagan voters stay home in 1984, that would hurt--particularly if a couple of million 1980 non- voters come out and vote against the president. That would put him below 50 percent of the vote. Compensating for that, Reagan strategists argue, would be support from people who used to consider Mr. Reagan trigger-happy. The Korean Air Lines incident, whatever else it does, provides strong evidence that he is not. But it's not clear whether this new support will offset any votes the president has lost.

Still, it seems that the thunder on the right is manageable so far--and probably inevitable. A president cannot run for reelection on the same kind of platform and with the same approach to issues that a challenger uses. A challenger--candidate Reagan in 1980--can rail against things as they are. An incumbent will be held responsible for things as they are. In the direct-mail business, Mr. Viguerie raises money by rubbing raw the sores of discontent, by persuading people that the sky really will fall, unless they send in their $15 now. Mr. Reagan can't win a second term with a similar appeal. Most incumbent presidents have had problems with their political bases. Mr. Reagan's cannot be dismissed as negligible, but so far he seems to be weathering them pretty well.