The letters, some scrawled on notebook paper, others typed on professional stationery, arrive daily at the offices of Virginia state senators bearing the same message: politics has no place in the debate about raising the drinking age.

But many senators, grappling with Gov. Charles S. Robb's proposal to raise the legal drinking age from 18 to 21, say election-year politics are central to the controversy.

"This whole thing has become the biggest political football this session," said one Northern Virginia lawmaker who reluctantly supported Robb's bill, which passed the House and now awaits Senate action.

The Robb bill has strong grass-roots support, particularly in Northern Virginia, the site of an active Mothers Against Drunk Driving (MADD) chapter. Nevertheless, some senators, particularly those who represent the state's college towns and Tidewater, which has a large military population, call Robb's bill punitive and unenforceable. Instead, they favor raising the drinking age to 19.

Virginia currently has three different minimum drinking ages: one must be 18 to drink beer in bars, 19 to buy it in grocery stores and 21 to buy wine or hard liquor.

Recently, a Senate committee, angry at Robb's refusal to compromise, killed two Robb-supported bills that would have raised the drinking age to 21. After the vote, Edward Kunec, president of Northern Virginia MADD, said he thought the governor should compromise in order to get a bill passed this session.

Such statements only serve to infuriate further some downstate legislators like Sen. Dudley J. Emick Jr. (D-Botetourt), who regards the Robb-backed proposals as "arbitrary" at best and "legislative chicanery" at worst.

"Those people who so religiously believe 21 is really going to save lives--then why aren't they saying, 'It's 21 across the board or nothing'?" said Emick, who favors making 19 the uniform beer-drinking age.

Supporters of a minimum age of 21, among them National Transportation Safety Board Chairman Jim Burnett, who has traveled here twice to testify, say experience in other states shows that raising the drinking age reduces teen-age drunken driving accidents.

Statistics compiled by Virginia highway officials in 1981 suggest that the issue may be more complicated, however. Those figures show that 6,292 drivers between the ages of 20 and 24 were involved in alcohol-related crashes, compared with 4,724 drivers between the ages of 16 and 19.

Those statistics have prompted Del. Samuel Glasscock (D-Suffolk) to propose raising the drinking age to 24. His measure was resoundingly defeated after evoking snickers from his colleagues, as did his bill requiring drivers to wear seat belts.

"It occurred to me after all this hoopla over 21 that if we were really serious about safety on the highways we ought to do something," said Glasscock. His seat belt bill never made it out of a House roads subcommittee, despite testimony by state Safety Director John Hanna that it could save an estimated 400 lives in the state annually.

A similar fate befell a bill sponsored by Del. James Almand (D-Arlington). Last week, the House killed his proposal to make those caught drinking while driving subject to a $100 fine.

Almand's bill outraged some of his colleagues who said they saw nothing wrong with drinking a beer while driving. Among them was Del. V. Thomas Forehand Jr., a Tidewater Democrat who voted to raise the drinking age to 21.

"I know legislators, I know lawyers, I know bank presidents and I know doctors who frequently stop to buy a six-pack on the way home," said Forehand, who called Almand's bill "ridiculous."

He was joined by Del. Frank Slayton (D-Halifax) who protested that "somehow we've gotten the idea that anyone 21 or younger is going to be a menace to highway safety simply because they have a beer in their hand."

"I couldn't believe what I was hearing," Glasscock said later. "All we're really saying with this drinking age thing is that the public is all excited about age 21 which is a group that doesn't vote in large numbers anyway. But when it comes to drinking in cars or wearing seat belts--things that affect us all--well, we've just decided we don't want to do anything about that."