Andrew P. Miller, Virginia's Democratic Senate candidate, climbed aboard a plane one day last week to meet his wife, Doris, whom he had seen only briefly for several days.

"It's good to see you," he said with uncharacteristic softness.Then he fell asleep.

Exhaustion does not come easily to Andy Miller. His campaign schedule covers most of day and generally leaves behind a trail of bleay-eyed aides and reporters. The press is always watching, waiting for the kind of mistake that has focused attention on his Republican opponent, John W. Warner, recently.

It doesn't happen.

With Andy Miller, a highest-honors Princeton graduate, number one in his class at the University of Virginia Law School where he set academic records, it is all business, and he gets indignant when the sincerity of his campaign talk is questioned.

Miller called a press conference last week, for instance, to discuss Soviet American relations and the Strategic Arms Limitation Talks, then opend the floor to reporters.

First question: "Do you think Virginians really car about SALT?" Of course, Miller insisted, and then launched deeper into SALT details.

Then he was off to the next appearance, scribbling notes to himself on what he feels are the issues - inflation, defense, taxes and a balanced budget.

There is little room for humor in a campaign in which the candidate logs hundreds of miles each week cris-crossing Virginia with the message that the issues are important. Andy Miller says Virginians tell him that, but it often seems to be the other way around.

He does not laugh at stories or jokes about his oppenent, but laughs uproariously when a television interviewer asks him to relax.

One night, as his plane descended slowly toward Bristol, the radio crackled a warning that somebody had already mistaken a nearby highway for the runway and had landed there. Everybody laughed except Miller, who nevertheless said he thought it was very funny.

"I wish Andy would talk more about Warner's mistakes," one supporter complained last week. Miller has been talking more about them lately, but sometimes the talk gets squeezed by rhetoric about inflation and taxes.

At a Buckingham County rally in the heart of Southside, where more than a hundred old-line Bryd Democrats gathered Watkins M. Abbitt, their political archbishop, took to the back of a shiny pickup truck to extoll the virtues of Miller, "a Virginian we all know."

"And somebody who doesn't want the tape erased," a farmer in the crowd chrotled, referring to a television interview that Warner requested be retaped so he could revise a statement he made indicating that he slowed integration in the Navy.

The crowd laughed warmly, and it seemed the perfect moment to seize the Warner issue. But when Miller's turn came, he launched back into taxes and inflation, and the crowd began edging toward the Brunswick stew.

If his speeches are not dynamic, Miller still has a rapport with the crowd that often is saved by the fact that he is no stranger to most Virginians, especially as a campaigner.

Because he has run for statewide office four times in the last nine years - twice successfully as attorney general, once as the loser in a gubernatorial primary race and now as a Senate candidate - he often is received like an old friend.

"Hey, Andy!" someone called out at an Arlington reception last week, and Miller and the man held a five-minute chat on campaign news. Later, Miller admitted he was not sure who the man was, but it did not matter. The important thing was that people do not introduce themselves to Miller. They just assume he knows them, which he seems to enjoy.

Miller is accessible. He is at his best when shaking hands. He's not the baby-kissing type, but he is earnest, especially in a one-on-one situation.

Miller is very conscious that the election is barely two weeks away. Lately he was been thumping hard on the fate of former senator William Spong in the last few weeks of his 1972 campaign for reelection.

Spong lost after William L. Scott, the GOP nominee, undertook a last-minute media blitz, much as Miller fears Warner will do.

Perhaps because of that Miller has added more stops to his already tough campaign schedule, an addition burden that he seems to welcome.

Campaigning, Miller said last week, is "sort of like running the Marathon."