An exberant Lillian Carter, proclaiming that "God is behind" her son, yesterday brought the Carter campaign message to 150 cheering supporters in Leesburg on her eighth Virginia campaign stop in three days.

"Y'all remember to vote for Jimmy," the 81-year-old Miss Lillian told the group crowded into a Leesburg inn for a $10-a-plate breakfast of biscuits and ham. "I came all the way here, and I almost forgot to tell you."

Wearing a blue pantsuit and a short fur coat, Mrs. Carter signed autographs for the enthusiastic crowd of Northern Virginia Democratics against a country music background. Then, before her audience and in a later meeting with reporters, Mrs. Carter launched into the string of one-liners that have made her a popular figure on the campaign lecture circuit.

On campaigning: "It's all right for good-looking men to kiss me, but I'm not crazy about kissing women. I love them, but I don't kiss them."

On her son Jimmy: "I never see him. If you see him, tell him I said hello."

On herself: "Sometimes I can be quite dignified, but I don't know when."

Mrs. Carter's Leesburg visit, aimed at lining up delegate support for her son, came as Virginia Democratic leaders predicted yesterday that Carter will command the Virginia delegation on the first ballot at the party's naitonal convention this summer.

An estimated 25,000 Virginians are expected to assemble at mass meetings around the state next Saturday to begin the lengthy process of selecting the state's 64 Democratic delegates.

"I think we're going strong all over the state," said Carter's state campaign chairman, George H. Gilliam, adding that he sees a "good, substantial majority" for Carter.

Leesburg Democrats echoed that assessement. "Carter's going to carry Virginia this year, and you can quote me on that," said an obviously pleased Del. Earl L. Bell D-Loundoun), standing with well-wishers in the 220-year-old Laurel Brigade Inn after Mrs. Carter had left with her entourage in a green and white camper.

Carter narrowly lost the state to former president Ford in 1976, but Bell said Ford's recent withdrawal from this year's presidential race will ensure that Carter can take Virginia easily.

Supporters of Sen. Edward M. Kennedy were quoted yesterday as saying they hope to surprise the Carter forces by knocking off 20 percent of the Virginia delegates and maybe more. Kennedy campaign officials said their strongest support lies in Northern Virginia's 8th and 10th congressional districts, and in the Tidewater area.

The a brief question-and-answer period conducted in a bedroom of the inn, Mrs. Carter admitted that she wasn't concerned about the issues of the presidential campaign ("I know so little about them"), but insisted her son is the best qualified candidate for the job.

"He's the competent candidate. He's the intellectual candidate," Miss Lillian said. "He's a Christian and God is behind him.'

In the face of criticism of the preisdent's economy policy, Mrs. Carter maintained that the nation's economy, with a projected annual inlfation rate of 18 percent, is "no worse than its always been."

"Every time inflation goes up, my Social Security payments go up a little bit too," she said.

While Mrs. Carter's performance met with widespread approval from her Leesburg audience, at least one obsrver, retiree Floyd Johnson, had to go home disappointed.

"I wanted to kiss Miss Lillian on the check, and she wouldn't let me,' said Johnson, who said years ago he had kissed the wife of then-president Calvin Coolidge at a campaign stop. "I had kissed a president's wife, and now I wanted to kiss a president's mothr.

"If I can find her again, I'm going to kiss her whether she wants to or not."