ANNAPOLIS, DEC. 22 -- Freshman Rep. Tom McMillen (D-Md.), bolstered by an endorsement and appearance with presidential candidate Sen. Albert Gore (D-Tenn), today became the fourth member of Maryland's congressional delegation to file for reelection.

McMillen, whose 4th Congressional District includes Anne Arundel County and parts of Howard and Prince George's counties, said his campaign themes are better education, a strong defense, protecting the environment and balancing the budget.

"I pledged to be a congressman of the people," McMillen told supporters at a breakfast held after several Maryland legislative leaders endorsed Gore's presidential bid. "I have a high standard to maintain."

McMillen said he has about $100,000 in the bank for his reelection bid and hopes to raise an additional $250,000. Aides said he still owes $100,000 from the 1986 race, which cost about $900,000.

Gore and McMillen endorsed each other's respective campaigns, and the presidential candidate asked McMillen supporters to help him in his bid for the White House.

McMillen, whose district includes several military installations, said he backed a defense initiative just adopted in the federal budget.

McMillan won a razor-thin victory in 1986 over Robert Neall, who was minority leader of the Maryland House of Delegates.

Earlier this week, GOP Rep. Helen D. Bentley, whose 2nd District includes most of Baltimore County, and 8th District Rep. Constance A. Morella, a Montgomery County Republican, filed for reelection. Democratic Sen. Paul S. Sarbanes, a two-term incumbent, also has filed for reelection.