President Reagan's transcontinental trek this week was nicknamed by reporters the "Spuds and Suds" tour, with stops in Boise and Milwaukee to campaign for Senate Republicans. Although he looked tired at the end of the grueling 12-hour expedition, Reagan had been true to form, making interesting detours from the prepared script of the day.

For example, as Air Force One flew to Idaho, word was passed to reporters that Egyptian President Hosni Mubarak could not expect an apology from the United States over the interception of the Egyptian airliner carrying four hijackers of the Achille Lauro cruise ship.

This was not exactly advertised -- reporters were informed under "deep background" rules that supposedly barred them from attributing it to anyone in the administration.

Reagan had not been on the ground in Boise more than a few minutes when he broke the ground rules. Asked if he planned to apologize, he shot back, "Never."

The president, who meets Soviet leader Mikhail Gorbachev next month, also departed from his prepared remarks at a fund-raiser for Sen. Steve Symms (R-Idaho) for this observation:

"You know, I've read a lot of the constitutions of other countries, including the Soviet constitution. And I was amazed to find that it has a lot of things in there that it promises that our own Constitution promises. Of course, they don't keep those promises over there, but they're in there."

Reagan later flew to Milwaukee to raise money for Sen. Robert W. Kasten Jr. (R-Wis.). It was after dinner when he spoke, and for all the talk about a possible compromise with Gorbachev that may restrain his Strategic Defense Initiative, Reagan was passionate in impromptu remarks about the prospects of making nuclear war obsolete.

Reagan said his goal is to "prove and establish" with research that a defensive weapon can effectively shoot down missiles. "Then we really can do away with nuclear weapons in the world once and for all because they will be useless from then on."

Reagan told a story about United Nations Ambassador Vernon A. Walters on a recent mission to China. The Chinese, he said, were critical of the defense proposal. "And then one of the government officials there said to him, 'We have a problem here in China that we often speak of.' He said, 'If a man has invented a spear that can penetrate any shield, and another man has invented an impenetrable shield and they meet, what happens?'

"And Ambassador Walters said, 'I don't know the answer to that. But,' he said, 'I do know what happens if a man with a spear that can penetrate anything meets a man who doesn't have a shield at all -- I know what happens then.

"They sort of changed their mind about our defense program," Reagan concluded.