For a national figure with presidential ambitious, Senate Minority Leader Howard H. Baker Jr. finds himself in a highly unusual position today: he has five opponents in the Republican Senate primary.

One, Harvey Howard, a former state coordinator for the John Birch Society, has labeled him "a traitor." Another, James D. Boles, has accused him of ignoring "the needs, wants and desires of the people of Tennessee."

The reason for the attacks centers on Baker's support of the Panama Canal treaties.

None of his opponents is expected to give Baker serious trouble, but his chief aides are estimating they may collectively win as much as 30 percent of the vote - which would prove a mild embarrassment to the two-term senator.

None of the three leading Democratic candidates, who also opposed the treaties, was well-known before the race. They are Jane Eskind, the first woman to make a serious bid for the Senate in Tennessee history; Bill Bruce, a former state legislator from Memphis, and J.D. Lee, a flamboyant attorney who got into hot water with the Treasury Department for printing thousands of $100 bills with his picture and the slogan "Join the Tax Rebellion" on them.