John Kerry's political education is far deeper than that of senators who have merely legislated. He has journeyed to the heart of darkness many times and emerged to tell the tale.

It was not simply that Kerry's commander in Vietnam was the model of the blood-thirsty bombastic colonel in Apocalypse Now. Kerry's combat experience didn't end in the Mekong, but moved into the dangerous realm of high politics.

From his first appearance on the public stage, giving voice as a decorated officer to the anti-war disillusionment of Vietnam veterans, when Richard Nixon and his dirty-tricks crew targeted him, he has uncovered cancers on the presidency.

This is why the Bush administration fears him. He has explored the dark recesses of contemporary history, often without political reward. Tarred as a "flip flopper" by Bush's $85m TV ad campaign, Kerry in fact is one of the most consistent politicians of his generation.

In his first month as a senator, in January 1985, he discovered the thread that would unravel the Iran-contra scandal - the creation of an illegal foreign policy apparatus run out of the national security council by Reagan's military aide, Oliver North, and the CIA director, William Casey.

Kerry had the training and instincts of a prosecutor. As a district attorney in Massachusetts, he smashed the local mafia. Now, as senator, he has surrounded himself with tough investigators. In south Florida, they found men accused of drug-running who were shipping guns to the Nicaraguan contras and claiming to be instructed by the NSC.

They tracked down a contra adviser in Costa Rica known as "Colonel Flaco", who had evidence that North was involved in financing the contras with Colombian drug money. The path led further, to Panamanian dictator Manuel Noriega and to Saudi funding sources.

Kerry won support from Republicans on the Senate foreign relations committee to launch an official investigation, in large part because of the drug aspect. (Concerned about heroin addiction among Vietnam veterans, Kerry had followed the geopolitics of drugs.)

North learned of Kerry's work and told the Secret Service and the FBI that Kerry was protecting a possible presidential assassin. The FBI harassed "Flaco" and determined he was no threat, but he was intimidated into silence.

Republican staffers leaked information about Kerry's investigation to the Reagan White House and justice department. An assistant US attorney in Florida, prosecuting a case based on Kerry's leads, was ordered by the justice department to drop the matter. Virtually the entire Washington press corps dismissed Kerry's effort as a fantastic delusion and ignored it.

In October 1986, Kerry questioned the neoconservative assistant secretary of state for Latin America, Elliot Abrams, who brazenly lied about foreign funding for the contras. This testimony led, in time, to Abrams pleading guilty to a felony. (He was pardoned by Bush Snr and is now NSC chief for Middle East policy.)

A month later, the Iran-contra story broke in a Lebanese newspaper. However, Kerry was excluded from the congressional investigating committee for the sin of having been prematurely right. As consolation, he was given chairmanship of the subcommittee on terrorism, narcotics and international operations.

After three years, he reported that "individuals who provided support for the contras were involved in drug trafficking; the supply network of the contras was used by drug trafficking organizations; and elements of the contras ... received financial and material assistance from drug-traffickers. In each case, one or another agency of the US government had information regarding the involvement, either while it was occurring, or immediately thereafter."

Kerry's work on the contra-drugs connection led him to discover a link to BCCI, an international banking operation that was a front for drug running, money laundering and terrorism.

He launched an investigation that exposed its criminal "corporate spider web" in 1992. His report pointed to new areas that should be investigated, including "the extent to which BCCI and Pakistan were able to evade US and international nuclear non- proliferation regimes to acquire nuclear technologies".

From Vietnam onwards, Kerry has probed the inner recesses of government, pursuing a persistent and cumulative investigation into the underside of national security and terrorism.

If the Democrats had held the Senate for a sustained period of time, his proposal to regulate the world of money laundering, which was not enacted, might even have helped stymie Al Qaeda.

He has experienced the abuse of justice; had his patriotism impugned; battled enemies foreign and domestic; tried to restore accountability; and fought on, down to today - which is why he is running for president. -Dawn/The Guardian News Service.