Fred Thompson's early political career

As a non-American I didn't know much about Fred Thompson's political career at all- seems though that his career dates far further back than his position as a senator in the 1990s- he was involved apparantly in the prosecution of Richard Nixon, leaking information from Congress to the adminstration. Obviously this throws light upon Thompson's political positions- but for an uninformed source on US politics, it makes me wonder about Fred Thompson's wider political credentials- he seems more political than we thought!