BALTIMORE -- Democratic candidates Clarence (Du) Burns and Kurt L. Schmoke are entering the final weeks in the race for mayor here, and voters are faced with a historic option: For the first time they will choose between two black candidates for their chief executive.

This port city of 780,000 is among the last of the predominantly black metropolises in the country to elect a black mayor, due in part to the long and popular reign of William Donald Schaefer, now governor of Maryland. Baltimore's population is about 55 percent black.

But unlike many other cities, including Chicago in 1983 and Philadelphia this year, where white and black candidates have been pitted against each other in often-polarizing struggles, Baltimore has no major white challenger in the Democratic primary Sept. 15. With 88 percent of the voters registered as Democrats, the primary is considered tantamount to election here. No major Republican candidate is seeking the office.

In Baltimore, the two generally liberal candidates themselves speak to a new phase in black politics. Burns is a rough-hewn, high school-educated pol whose career advanced because of his success at machine politics, and who might have expected the four-year term as mayor to be his for the asking. But he faces an uphill battle against Schmoke, the Ivy League prosecutor whose resume appeals to white and black professionals and whose law-and-order stance is attractive to poorer blacks in neighborhoods besieged by drugs and crime.

So far, Schmoke is running far ahead of Burns in opinion polls, and interest in the race appears to have sagged. Tonight at 8, the two face each other in a one-time television debate (WMAR, Channel 2), which could reignite some interest.

The absence of a white candidate in the race has created a political anomaly: two black candidates fighting over white working-class voters -- Schmoke's weakest source of support and a last hope for Burns.

Nowhere is this more evident than in the white working-class enclaves of Baltimore, those strongholds of old-line Democratic clubs and machine politics that traditionally vote conservative.

Burns, the 68-year-old incumbent who fought his way from high school janitor to the top of the political heap, is very much a part of that old system. A political disciple of Schaefer, Burns ascended to the City Council presidency and then automatically inherited the mayor's post when Schaefer moved to the State House in January.

But after months of campaigning he still has the underdog status. As a result, he is counting on his friends in the row houses of Hampden, Highlandtown and Locust Point -- neighborhoods that encompass a mix of Polish, Italian, German and other ethnic groups -- for crucial help in what he says is the last election he plans to enter.

Coupled with that, Burns strategists are counting on what they perceive as a latent distrust among blue-collar voters of sleek, monied candidates with fancy academic credentials -- in a word, Kurt Schmoke.

Schmoke, 37, currently Baltimore state's attorney, exudes a clean-cut scholar-athlete image: championship high school quarterback, captain of the Yale football team and Yale's first black senior class president, Rhodes scholar, Harvard law school graduate, one-time White House aide and member of a blue-chip Baltimore law firm before he entered politics in 1982.

In that year, he defeated white conservative William A. Swisher for the state's attorney's post.

Swisher drew heavy support from the white working-class neighborhoods of Baltimore. These are the same neighborhoods that Burns is now courting in his fight against Schmoke -- an irony that is not lost on Burns strategists.

"It's two different situations, but the votes will be the same," Burns deputy campaign manager George Guest said with a wry smile.

Schmoke's impressive credentials and well-oiled campaign could work against him, Guest said. "It's too smooth," he said in an interview. "It's too well-financed. People are saying who's really running the show" -- a reference to a foray to New York by Schmoke in March "Kurt has to work real hard {to win a blue-collar neighborhood}. They're cautious around people with college degrees. They think he might be too good to get his hands dirty."

-- Schmoke supporter James W. Campbell

to solicit campaign funds from prominent socialites, philanthropists and others.

Burns, with his no-frills manner and comfortable familiarity in the city's political clubs, is far more appealing to the average white ethnic working man, said Guest.

"There's no question, he's got the support," Guest said, noting that key Democratic clubs in Highlandtown in East Baltimore and Hampden in the north central section of the city have endorsed Burns.

"People feel more comfortable with Du than with Kurt," said Dominic (Mimi) DiPietro, city council member and crusty 82-year-old patriarch of the United Democratic Club in Highlandtown.

Burns attempts to capitalize on his humble background, noting at political rallies in working-class neighborhoods that, like him, neither Abraham Lincoln nor Harry Truman went to college.

Schmoke supporters brush aside such comments. "The Burns people misunderstand those communities," said Schmoke campaign manager Larry Gibson, a professor at the University of Maryland Law School. "People there respect education and hard work. The Burns people do them a disservice."

Furthermore, if the Burns people want to argue over "who comes from the most humble origin," Gibson said, they should keep in mind that Schmoke grew up "in a working-class family . . . and worked in a pipe mill in the summer" to help support the family.

Del. James W. Campbell (D-Baltimore), a Schmoke supporter who represents the Hampden area in the state legislature, acknowledged that "Kurt has to work hard to {win} an area like this . . . . They're cautious around people with college degrees. They think he might be too good to get his hands dirty."

Nevertheless, Campbell said, Schmoke campaigned door-to-door Wednesday night in the heart of Hampden, the scene of a racial melee last spring at a neighborhood school, and was "very well received . . . . People change their minds when they meet him."

Across the city in Highlandtown, Del. American Joe Miedusiewski (D-Baltimore) said Schmoke has been cordially received. "It's just that Du is more familiar with the people," he said.

Whichever way the election goes, Miedusiewski said, "it's a no-lose situation. We'll have a good mayor."