Virginia's Republican gubernatorial nominee, J. Marshall Coleman, has finally found an issue that, he said, "very clearly separates me from my oppponent." That issue is supposed to be crime.

But an examination of the respective position papers on crime of Coleman and Democrat Lt. Gov. Charles S. Robb, both conservative laywers with similar views on most issues, fails to reveal sharp differences. Both men, for example, quote Chief Justice Warren Burger on the need for a crackdown on criminals.

Coleman talks tougher: "Criminals must go to jail and stay there, with no early release," the GOP candidate wrote in a treatise entitled "Communities Against Crime." In Robb's statistic-laden "plan on law enforcement," the Democrat said: "It is essential that criminals with a prior history of criminal activity be punished severely for repeat offenses."

Behind the bumper-strip slogans, however, are two well-thought-out proposals whose contrasts are better measured in shades of gray than in the stark black-and-white of Coleman's rhetoric.

The principal difference is in their approach to criminal sentencing. And even in that area, both men agree that current practices result in disparities. But they differ on how to remedy the situation.

Coleman wants to narrow the range of penalties that a judge or jury may impose for specific crimes, while Robb would encourage uniformity of sentences by providing judges with computer information on sentences being imposed by their colleagues throughtout the state.

Each has critized the other's approach.

Robb, writing of himself in the third person, said, "Robb refuses to apply simplistic solutions based on political expendiency. . . .for such an approach only aggravates the problems."

Ridiculing his oponent's approach, Coleman said Robb "has scorned a system of uniform sentencing that will see to it criminals are punished, that they go to jail and serve their sentences. He has said instead that we should strive for uniformity in sentencing by giving judges computers."

In a position paper issued last Monday, Coleman cited a 1977 State Crime Commission report which said "a definite geographic disparity exists within Virginia for certain crimes." For example, it found that the average sentence for robbery in Alexandria was seven years and two months, but in Bedford it was 32 years and two months.

Coleman told of a case in Arlington in which two men together broke into an apartment and raped the two women who lived there. While the evidence against them was the same, they were tried before different juries. One defendant received an 11-year sentence and the other 218 years.

"Disparities like that undermine our entire criminal justice system," Coleman said.

To insure that "persons who commit like crimes will receive like sentence, and serve their full sentences with no early release," Coleman would ask the legislature to enact a uniform sentencing law.

It would narrow the broad range of penalties available within 10 categories of crimes and establish presumptive sentences for specific crimes. In instances where extraordinary circumstances exist, judges or juries could vary the sentence if they explained why they were doing so.

Coleman's idea isn't new: He proposed three versions in recent sessions of the legislature, but the Democratic controlled body, encouraged by many members of the judiciary, rejected all of them.

Democrats are quick to point out that this year it was Republican State Sen. Herbert Bateman, who may have been Coleman's first choice as his lieutenant governor running mate, who blocked the legislation.

Robb believes the state should "strive for uniformity while retaining the human element and community input into the sentencing process."

To Coleman, "it's state law, not community standards, that must be applied."

Coleman's call for "no early release" prompted a person who works with inmates at the pentitentiary in Richmond to criticize the attorney general for "appealing to the red necks who want to lock'em up and throw away the key. But if the inmates didn't have a chance for parole, you wouldn't be able to find guards crazy enough to work in the prisons. The inmates would riot, they'd burn down the prisons."

In an interview, Coleman said, "I'm not trying to kid anyone. Good time must be in there to make the prisons work." He would retain the system that allows prisoners who exhibit good behavior to cut 10 days from their sentence for every 20 days served. What he opposes is the practice of automatically releasing inmates six months before the completion of their sentences.

"I want a time certain -- no ands, if or buts," Coleman said.

"There should be no second-guessing by the parole board. I'd like to put a chart in every grocery store -- a truth in advertising sign -- that shows 'this is what you get for armed robbery, burglary, and so on.'"

The two candidates also agree that the parole system needs reforming.

Coleman would like to see the parole board become "a placement agency," stripped of its ability to decide which inmates should be released early. The current situation "forces inmates to be actors. It has made our prisons drama schools. An intelligent but surly first offender may get passed over in favor of a really bad guy who 'got religion,'" Coleman said.

Robb admits that the parole system is "not perfect," but calls it the best and fairest way to handle parole. His reform would be limited to staggering the terms of the five members of the parole board, to reduce the influence of a single governor.

By week's end, the "clear difference" which Coleman had discovered had nearly been obscured by an exchange of charges between his staff and Robb's about their respective positions.

The Robb camp accused Coleman of being inconsistent on the subject of early release, charging that as a member of the state Senate in 1976, Coleman twice voted for a bill that permitted prisoners serving life sentences to be paroled after serving 15 years, and those serving two or more life sentences to be paroled after serving 20 years.

Coleman's staff responded by saying "Chuck Robb's staff should learn how to read legislative bills." The language cited by the Robb staff was part of a bill that was being amended to add time to the minimum that must be served on a life sentence, according to Coleman rejoinder.

The chief sponsor of the 1976 amendment, State Sen. A. Joe Canada of Virginia Beach, weighed in with his own attack: "Frankly it's embarassing to discover that the presiding officer of the Senate [the lieutenant governor] and his staff can't read legislation properly." But Canada is hardly a neutral observer, having lost the lieutenant governor race four years ago to Robb.