There was just a trace of disappointment in Idaho Gov. John Evans' voice, but he said he understood. The president of the United States is after all, "a very busy person leading a pressure-packed life," and the White House didn't feel it was advisable to mix politics and a holiday together."

"I had oh so many people say "good for him," said Evans. "He needs it."

Evans had been turned down in his efforts to involve President Carter in a political fund-raiser here during the president's vacation. When that didn't work, he said he suggested "a rather large nonpartisan reception." They turned him down on that, too.

Evans did get to ride in Carter's limousine during the 15-minute motorcade from the Boise airport Monday to the president's hotel, and while they discussed many of the controversies that have made Carter so unpopular in the West Evans did not get the Carter endorsement of his reelection that the local press kept asking him about.

"I didn't think it was appropriate" to ask for the support, Evans said. "We were told that this was his vacation right from the start."

It is, indeed, the president's vacation.It is also in many respects a test of whether it is possible - in the face of local political pressure, the insatiable demands of the press and the need for instant communications - for a modern-day president to take a real vacation, to get away from the presidency for even two weeks.

When the president showed up in church Sunday morning when he was in Plains, so did the reporters brought along in station wagons by the White House press office. When he went to an old friend's home for dinner there, the press was outside drinking beer and soda and eating hamburgers.

When he arrived in Boise, an Idaho Stateman editorial greeted him. The president's failure to mix with Idahoans during his visit, it said, would reinforce "a strong feeling that many easterners view our state not as a place where people live, but as a special preserve, a place toset aside to be enjoyed by visitors, then put back on a shelf and preserved until the next trip out."

And, as Carter and his family and Interior secretary Cecil D. Andrus and his family departed yesterday morning for their secluded three-day raft trip down the Middle Fork of the Salmon River, there were advance security people in kayaks ahead of them, a Strategic Air Command plane out of sight above them for communications, and a satellite geared up to handle any other communications needs.

An elaborate media ballet, arranged by the White House press office, also got under way as the pools of eight reporters and technicians assigned to cover the trip grouped.

It went like this:

8 a.m.: pool 4 arrives river to preposition at footbridge.

8:25. pool 5 arrives river departure site.

8:30: the president arrives river raft departure site.

8:55: President's raft passes under footbridge, press pool 4 coverage.

9:20: pool 4 takes all filing and photo materials from pool 5, boards chopper and departs.

9:25: pool 5 boards raft and departs downriver.

The press raft, accompanied by a White House staff raft, was not expected to see much of the President during the trip down the river because of his desire for privacy.

But they may have seen even less because it rained intermittently as the president departed and later in the day the rain on the river turned to intermittent hail and snow bad enough to prevent huge Marine helicopters from dropping off or picking up reporters.

"How'd you like to wake up at your camp site one morning, get out of your sleeping bag all bleary eyed and messy. adn find TV camera lenses and 20 million Americans staring right in your face," said one White House aide on the trip.

But the president is the president, and not just an ordinary camper. The Idaho Statesman, excluded by the White House from the national media pool, is planning its own form of coverage, which editors there declind to outline. However, some reporters noted that while aircraft flights over the president are prohibited, experienced hikers could trek with mules or horses to the edge of the river for coverage.

The President and his staff see the Idaho trip, as well as the Wyoming visit following, as in part an effort to pay tribute to the Western states where his popularity was low in the campaign and went even lower after his cancellation of many western water projects.

Gov. vans said he believed the tip would help in that effort, despite Carter's search for secluison. "He's going to be stronger after this trip than he was before," Evans said, crediting an airport new conference held by the president on his arrival for much of that.

"I was as concerned as everyone else about how much personal contact there was going to be. Some of this advanced people indicated there would be none. But it was just the opposite at the airport," Evans said.

He conceded, however, that Carter would unquestionably lose the state if the election were held today, as he lost it in 1976. "He's going to be mending fences for a long time in the West," Evans said.