Presidential hopeful John Glenn came here courting Virginia's Democrats at the party's annual Jefferson-Jackson Day dinner tonight.

Glenn, who is generally regarded as a middle-of-the-road Democrat, is considered the favorite of Virginia's conservative Democrats, and he wooed the crowd of more than 1,000 with fervor.

But like a choosy belle with time on her side, the state's Democrats expressed enthusiasm for his company while carefully avoiding any long-term promises, and pointedly introduced a sweetheart of their own.

"Senator, last time you went on your orbit alone," said Lt. Gov. Richard Davis to the former astronaut. "This time," Davis suggested, pointing to Gov. Charles S. Robb, "I've got a good copilot for you."

"President Glenn and Vice President Robb," intoned Virginia Attorney General Gerald Baliles during his stint at the podium.

Being the keynote speaker at the Jefferson-Jackson Day dinner here in a prepresidential election year means everyithing or nothing, depending on whom you ask. Most state party officials say Glenn was chosen because he draws a crowd, and they emphatically deny that his selection amounts to an endorsement.

Robb has said publicly that he is not interested in a vice-presidential spot on any ticket.

Introduced by Robb as "the man who just could be the next president of the United States," Glenn offered elaborate praise for Virginia's Democratic tradition, barbed criticism of the Reagan administration and a few quips about the much-discussed plan to nominate Robb as Virginia's favorite son in the 1984 presidential campaign.

Robb has said he would accept such a plan only as a means of to keep ing his state's delegation united.

"Almost everyone is talking about 1984," Glenn said. "I've heard people saying Virginia might even enter a favorite son candidate. That can mean only one person. But I checked with the governor, and University of Virginia basketball star Ralph Sampson isn't old enough."

Glenn's speech was enthusiastically applauded, particularly when he promised to "protect our constitution from extremist attacks . . . . We'd stop trying to grant favors to schools practicing racism as part of their religion.

"In the Democratic Party," Glenn said, "we don't confuse the Epistles of the New Testament with the Apostles of the New Right."

Glenn also called for a job-training program and for ending "the disgrace of soup lines by feeding the hungry with surplus food we're paying to store."

By night's end, state party officials credited Glenn with the sellout crowd and record-breaking net proceeds, estimated at $75,000.