Mike Synar, 45, the brash, bright and buoyant Oklahoman who represented the people of his state's 2nd District in the U.S. House of Representatives for eight terms before losing the Democratic primary for renomination in 1994, died of brain cancer Jan. 9 at his home in Washington. The cancer had been diagnosed in July 1995.

Mr. Synar, a lawyer, rancher and real estate broker from a prominent ranching family in conservative northeast Oklahoma, was first elected to the House in 1978.

During his years in Congress, he vigorously supported campaign finance reform, stricter gun control and environmental legislation. He also voted for higher grazing fees for cattle on public lands, and he seemed to find himself in opposition to the tobacco industry, ranchers and the gun lobbies.

In the 99th Congress, Mr. Synar led the House opposition to the Gramm-Rudman plan to reduce the budget deficit, a measure favored by conservatives and thought to be immensely popular in a district such as his. After losing the fight in Congress, Mr. Synar helped start legal challenges to the plan, which helped lead to a portion of the law being declared unconstitutional.

His stands were thought to be anathema to his conservative constituents, but they continued to back Mr. Synar until 1994. That year, he was upset in a primary runoff by a retired teacher, who went on to lose to Republican Tom Coburn, an obstetrician, in the general election.

But it seemed that Mr. Synar relished the good fight and never regretted a single vote. "If you don't like fighting fires, don't be a fireman. . . . And if you don't like voting, don't be a congressman," he once said.

In accepting the 1995 Profile in Courage Award from the John F. Kennedy Library, he said, "I believe that to be courageous is to be guided by your own internal compass, rather than popular decisions and the madness of crowds."

By his last term in office, he had become chairman of the Democratic Study Group, the party's liberal think tank. He also had become chairman of the environment, energy and natural resources subcommittee of the Government Operations Committee. He also ranked in the top third of the Judiciary Committee and the powerful Energy and Commerce Committee.

Facing little opposition in the 1992 general election, he spent time that year helping to coach then-candidate Bill Clinton for the upcoming presidential debates. Mr. Synar played the part of Ross Perot in mock debates.

After learning of his death, the president said: "Mike Synar was a brave and unflinching public servant who in tough political times remained true to his principles. He did not always do what was popular, but he always did what he thought was right -- for Oklahoma and for America. Throughout his life, and especially during the past six months, Mike Synar was a true profile in courage."

Sen. Don Nickles (R-Okla.) said in a statement that Mr. Synar was "an energetic congressman with very strong convictions who had a significant impact on national politics."

Mr. Synar was born in Vinita, Okla., into a family that the All-American Family Institute selected as the "Outstanding Family" in the United States in 1971. The young Mr. Synar became a two-time national 4-H champion. He was a 1972 business administration graduate of the University of Oklahoma and a 1977 graduate of its law school. He also received a master's degree from Northwestern University and studied at the University of Edinburgh in Scotland.

Only a year after settling in Muskogee, Okla., he defeated the incumbent congressman, Ted Risenhoover, in the Democratic primary.

Mr. Synar was ambassador-designate of the International Telecommunications Union. Also since leaving Congress, he had chaired the U.S. Bankruptcy Review Commission and been chairman of the Campaign for America Project, a nonprofit organization devoted to campaign finance reform.

Survivors include his father, a brother and a sister. CAPTION: MIKE SYNAR