It was a fitting exit from the Capitol for former governor Charles S. Robb, and, like his future plans, it was somewhat mysterious.

Moments after his successor, Gerald L. Bailes, was sworn in, Robb slipped off the inaugural stage into the State Capitol. His tearful family in tow, Robb vanished into the steam tunnels snaking under several buildings, leaving reporters to guess where he would emerge for a waiting car and ride to his house in McLean.

In his final hours as governor, the son-in-law of President Johnson kept to his game plan of turning aside questions about his political ambitions as he went about the mundane final chores of packing and plunging into the inaugural parties.

"It's sort of like following the corpse," joked Robb as he made one last pass through his third-floor offices where, during the past four years, he had earned the reputation of being one of Virginia's most popular and progressive governors.

Robb, 46, had been staying there until nearly 3 a.m. for the past several nights, even cleaning out his medicine cabinet.

"Except for a tube of toothpaste, it's clean as a whistle," he told Baliles during a joint appearance on Friday. "It's less than 25 hours before I become a has-been," Robb joked then.

Robb's characterization of himself hardly fits the aggressive political presence he is maintaining. Robb, who under Virginia law could not succeed himself, insists he has "no plans" to run for public office and is keeping up a steady stream of speeches and appearances outside Virginia only as part of his and other officials' efforts to moderate the national Democratic Party.

"I really believe the guy is a factor in '88," said state Sen. Dudley (Buzz) Emick (D-Botetourt). Emick has been a frequent critic of Robb's administration, but said today he believes that Robb's success has laid the groundwork for running for president or vice president.

"He's popular beyond political imagination," Emick said.

Robb, who lives in McLean, has joined Hunton & Williams, one of the nation's largest law firms, to practice in the District of Columbia and Virginia.

Following tradition, Robb limited his public appearances Friday and today to avoid detracting from Baliles' inauguration. But reporters dogged Robb's every move: when he received parting gifts of a bronze bell and a Canada goose, when he unveiled his official portrait, even trying to follow him into his private bathroom.

"I'm going to use the facilities," Robb said, "if you'll permit this one private moment."

For George M. Stoddart, Robb's press secretary, some of the questions became too detailed. Asked what Robb and his wife Lynda had for their last private dinner in the governor's mansion Friday night, Stoddart simply responded: "Food."

Robb, when asked what he and Baliles discussed moments before the inauguration, replied: "We discussed a number of items, as two friends might. They're normally shared privately."

At a prayer service this morning, Robb signaled the imminent change of power. He and his wife were led down a side aisle of the historic St. Paul's Episcopal Church, while Baliles strode purposefully down the center aisle.

In his office Friday afternoon, Robb had gone from room to room, greeting longtime state government workers and leaving hand-written notes to staff members.

"At 5 p.m. it was like the last day of school and people had just gotten their annuals," said Charles Sydnor, president of Emory and Henry College and a frequent speech writer for Robb. "People were laughing and crying."

Robb and his wife returned as private citizens to their house in McLean late this afternoon. In a flowerpot on the porch of their red brick home overlooking the Potomac, friends had stuck a small, brightly colored sign that said: "Welcome Home to: The Robbs."

Inside, boxes were piled high in each room.

"Our priority is to find him a pillow," teased Lynda Robb, pointing toward her husband. Robb said that the first thing he wanted to do was get a good night's sleep.