Days before registration closes, District voter rolls have swelled to an all-time record for a primary and close to the level that preceded the last presidential election.

Observers attribute the upswing to several highly competitive citywide party races and new efforts by the Board of Elections to make registration easier. They also caution that it may have little effect on voter turnout.

By early this week, 291,367 District residents had registered to vote, only about 8,000 shy of the record high of 299,757 before the 1988 presidential election.

The deadline for registering for the Sept. 11 party primaries is midnight Monday.

"This is a watershed election, and that has generated enormous interest," said Ronald Walters, chairman of the political science department at Howard University.

This year the District will elect its first new mayor since 1978, its first new House of Representatives delegate in nearly two decades, a new D.C. Council chairman and the first-ever "shadow" posts -- two for the U.S. Senate and one for the House. Moreover, the field of candidates is wide.

Two city programs also have helped elevate voter rolls. One, dubbed the "Motor Voter" program, has allowed D.C. residents to register when they apply or reapply for their driver's licenses. City officials say the program has been responsible for about two out of three new registrants since it began in May 1989.

Another new program this year sent all D.C. residents a return-postage-paid card to request registration forms or change their voter address. The city hired a coupon distributor to include the cards in packets of merchandise coupons, a move that produced 9,000 new registrants in two months, election officials said.

In the first six months of this year, more than 23,000 people registered, nearly six times the number who registered in the first six months of 1986, the last time the District held a mayoral election.

Political observers are careful to note, however, that more voters on the books do not always translate into more voters at the polls. Although the number of registered voters in 1988 was the highest of the decade, only 42 percent of voting age citizens actually cast ballots in the election, less than other years.

"Ease of registration increases opportunity to vote," said Curtis Gans, director of the Committee for the Study of the American Electorate. "It does not necessarily increase motivation to vote." He said that in Colorado, which introduced a "Motor Voter"-style program in 1988, registration increased 13 percent, but turnout in that year's general election increased by only 0.1 percent.

Because only people who have declared a party can vote in a primary, about 255,000 or 88 percent of the city's 291,000 registered voters, are eligible to vote in September.

In the 1986 primary, about 243,000 of the 273,000 registered voters were eligible.

The largest increase in registered voters has occurred in Ward 2, where registration has climbed 12.6 percent since 1986. Wards 1 and 3 followed with increases of 10.6 percent and 11.3 percent. Ward 8 was the only ward to lose voters, dropping 1,202, or roughly 5 percent.

Neither these changes nor the recent overall increases have altered the balance of registration among the city's wards, however.

Ward 3 continues to lead with more than 44,000 registered voters, or 15 percent of the city's total.

Party affiliation, however, has shifted slightly. Along the way, Democrats have gained 1,318 voters from the other parties and the Republicans lost 60.

The Board of Elections will remain open until midnight on Monday for anyone who wants to register for the Sept. 11 primary.

People who miss that deadline will have until Oct. 9 to register for the Nov. 6 election.