In style, rhetoric and even the choice of campaign consultants, Stewart Bainum Jr. has wrapped himself more snugly in the mantle of outgoing Rep. Michael D. Barnes than the other Democrats vying to succeed the popular congressman.

Today, three months before the primary election, Bainum campaign organizers are actively courting Barnes for a preelection endorsement, an unlikely event given Barnes' own intense struggle to win an open U.S. Senate seat.

Nevertheless, Bainum already has proclaimed himself heir to Barnes' tradition of being a national figure on foreign policy issues while maintaining solid ties to the 8th District.

The strategy has shown early signs of working. Bainum leads all candidates in fund raising, which has enabled the 40-year-old Takoma Park native to send mass mailings to thousands of prime Democratic voters in the district.

The mailings -- there will be at least two in June alone -- are the linchpin of Bainum's plan to expand his political base beyond the Silver Spring area he has represented in the Maryland General Assembly for eight years.

Elected to the House of Delegates in 1978 and to the state Senate in 1982, Bainum has forged a record that is liberal on many social causes and more moderate on fiscal issues.

He is perhaps best known for his successful campaign to strip the all-male Burning Tree Club of its state tax break as long as it bars women from membership.

Bainum, whose resume is studded with citations from such liberal interest groups as the NAACP, the Gray Panthers and Common Cause, contends that the Burning Tree legislation and other bills requiring the public disclosure of hazardous materials in neighborhoods have cost him some support in local development and business circles.

To offset that, he is touting his own achievements as an executive of Quality Inns Inc. and Manor Care Inc., two family businesses that have prospered into nationwide chains of hotels and nursing homes.

Bainum, heir to one of the largest financial fortunes in the Washington area, has said that being a millionaire with a social conscience comes easily to someone who attended religious schools for more than 17 years and then matured during the Vietnam War.

He said he has been driven chiefly by a desire to do good works in his community and also by an "ego drive" that spurred him on to higher political offices.

In the legislature, Bainum was no stranger to controversy, repeatedly needling Senate leadership during recent debates on the state's savings and loan crisis and making a doomed attempt in 1985 to trim the government payroll by 2 percent.

Over the past two years, he also has taken pains to improve his ties to organized labor -- a crucial bloc in Montgomery's Democratic primary -- by sponsoring such measures as a minimum income tax on corporations in Maryland. The measure failed on a tie vote in Bainum's committee.