In the good old days when Ronald Reagan was governor of California, he often answered accusations that he oversimplified problems by saying, "There are simple answers, just not easy ones."

Reagan takes his slogans seriously. And he usually has tried to live by this one.

On every issue from arms control, where he said he believed that a U.S. military buildup would force the Soviets into an agreement, to the federal budget, which he said he thought could be readily balanced, Reagan's proposals tend to be simple solutions simply reached.

On Lebanon, despite the skepticism of his military advisers, Reagan was sold on the simple solution that Syria and Israel could be induced to withdraw their troops and that the numerous warring factions would then allow the government to flourish. In September, 1982, when he sent the Marines into Lebanon for the second time, he said he believed that they could be home by that Christmas.

For Reagan, the invasion of Grenada was a simple decision that also appeared to be an easy one. It fit with his view that the United States should function as the guardian of democracy and with his conviction that the march of communism in the Western Hemisphere must be stopped.

"We're not going to lose a country to communism on our watch," Reagan's close advisers have quoted him as saying, and it became a favorite slogan inside the White House.

Grenada, a Marxist pimple in the eastern Caribbean, was to Reagan a festering sore that could corrupt the region. The airport runway that was being built by Cubans on the tiny island was to Reagan a pipeline through which the Soviets could fuel and arm outposts of the "evil empire" in Cuba and Nicaragua.

The opportunity Reagan saw for swift, successful action in Grenada occurred soon after the suicide-bombing of the near-defenseless Marines at the Beirut airport. Reagan reacted to the magnitude of the death and destruction of this event in personal rather than political terms. Those who saw him closely the next two days remarked on his tiredness, frustration and unhappiness.

"Never again will we send our boys to fight and die in a war we do not intend to win," was another slogan Reagan repeated during two presidential campaigns. He didn't know it wasn't that simple.

Whatever else one may say about him, Reagan cares about those under his command. He routinely has called parents of Marines killed on active duty in Lebanon, not to mention families of FBI and Secret Service agents killed in the line of duty in the United States. It would have taken 100 Reagans to perform this task after the Beirut bombing.

Compared with Lebanon, Grenada offered a wonderful opportunity for effective simplicity at lesser cost. There were Americans whom he said he believed to be in danger. There was a hemispheric outpost to be defended. There were communists to be replaced.

And the opportunity for what appeared to be a small, successful war came in the shadow of the Beirut disaster that had its origins in the simple-mindedness of leaving Marines exposed in what Reagan resolutely insisted was a "non-combat" role in Lebanon.

"No more Vietnams," Reagan liked saying repeatedly to the cheers of the faithful in 1976 and 1980. It was another of his favorite slogans. He should not be surprised--if he still chooses to run again--if his next opponent proclaims, "No more Lebanons."

The events in Lebanon and Grenada have confirmed the worst fears of Reagan's pollsters and strategists, who had hoped that economic recovery would be the dominant issue of the 1984 election. The only foreign-policy issue that interested them politically was arms control, particularly if it looked as if an agreement with the Soviet Union was achievable.

Issues on which voters had the least confidence in Reagan, perhaps appropriately, were Lebanon and Central America. The concern of his pollsters and strategists now is that Reagan's response in both situations will revive old fears of Reagan bellicosity that Democrats unsuccessfully tried to fan in 1980.

On the other hand, in a recent strategy memo for Democratic candidates, Washington-based political consultant Vic Fingerhut looked at presidential elections for the last 40 years and found that Republicans, with the single exception of 1964, benefited when campaigns focused on foreign policy and were hurt when domestic policy was the focus.

Fingerhut's message to Democrats was to "partisanize the 1984 campaign" and focus on Reagan's domestic policies. "Don't overestimate the damage that can be done to the Democrats if foreign policy predominates in the minds of voters on election day," he wrote.

Alibi of the Week: Speaking to the National Aviation Club, Rep. Norman Y. Mineta (D-Calif.) said, "I am sorry to have to speak and run today, but the House is having one of its particularly manic weeks, and I don't dare take my eyes off the chamber for more than an hour at a time. I might miss the invasion of a couple more countries."

Reaganism of the Week: Welcoming Bangladesh's military leader, Lt. Gen. Hussein Mohammed Ershad, to the Oval Office on the day of the Grenada invasion, Reagan said, "You left the dry season in your country to come here to the rain."