Joe Linus Barton from Ennis, Tex., admits it. Since he came to Washington three weeks ago, he's been nervous. Make that very nervous. "Gosh, a small-town boy like me coming to the big city," he said, with a southern twang, "and getting exposed to the inside workings of the government. Gosh, who would have ever thought?"

Joe Linus Barton, the vice president of a printing company and owner of a weekly newspaper in Houston County, is as excited as he is nervous. Barton is one of this year's 14 White House Fellows.

"Sometimes I still can't believe it," he said, shaking his head. "I can't believe I'm here."

About 1,650 people from across the country applied for the program. Those "gifted and highly motivated young Americans" selected work in the White House, on the president's or vice president's staff or with a Cabinet member. For them, the last several weeks has been a time of adjustment -- to their new jobs, new homes and the grand Washington social scene.

The fellows, along with 100 guests, gathered last night at the program's new offices on Jackson Place in Northwest Washington. "Beautiful, isn't it," said retired Vice Adm. James Stockdale, chairman of the White House Fellows, looking around the room.

Beautiful, yes. Comfortable, not quite. Unfortunately, the air conditioning was not functioning properly. But the guests tolerated the crowded, steamy party. Everyone wanted to see Lady Bird Johnson.

Lady Bird, however, never came.

Lyndon Johnson established the program in 1964. His wife, according to Stockdale, was equally committed to its success. A letter she wrote on March 1, 1973, hangs on the wall and throughout the evening many of the guests hovered around the message.

"Lyndon had such high aspirations for each of you . . . . The highest tribute you can pay him will be to make sure that his dreams -- and yours -- for the White House Fellowship Program become a reality through your own contributions to this wonderful nation in which we live."

The current fellows chatted with program alumni, as well as others who dropped in, such as Frank Hodsoll, the apparent anointed for the chairmanship of the National Endowment of the Arts, Tom Pauken of ACTION, Adm. Stansfield Turner, former head of the CIA, and William Webster, director of the FBI. A long list of notables had been invited, but there were two parties on the block. President Reagan was having a reception for business leaders at the White House.

Joe Linus Barton, assigned to the Department of Energy, looked around the room, as wide-eyed as a child at Christmas. "Boy, it's going to be a great year."