In special training camps, the Secret Service is preparing a small army of 1,500 agents to protect the biggest crop of presidential contenders in recent memory. And officials are worried that even this impressive number of highly trained bodyguards may not be enough, according to agency sources.

With eight Democrats and six Republicans planning to throw their hats into the ring, the Secret Service faces its biggest political protection assignment in history.

The reason for the large number of candidates is that this will be the first time since 1968 that an incumbent president isn't running.

That was also the year when the assassination of Sen. Robert F. Kennedy (D-N.Y.) led President Lyndon B. Johnson (and then Congress) to order Secret Service protection for all "major candidates" for president.

That choice of words has given the resolutely apolitical Secret Service a judgmental role usually assumed by pundits and party leaders.

How does the service decide who is a "major candidate" and who is not? Which contenders will acquire the instant prestige of Secret Service protection, thus certified as candidates to be taken seriously?

Agency sources have told us how the judgments will be made: An advisory committee of political pros will meet in November to make the determination. This unofficial committee will include the speaker of the House, the majority and minority leaders of the House and Senate (even though Senate Minority Leader Robert J. Dole {R-Kan.} will be a candidate), the treasury secretary (the Secret Service's boss) and an unnamed additional member chosen by the committee.

Protection of the designated candidates is scheduled to begin Feb. 1, 1988. Each contender will have two Secret Service teams assigned. The bodyguards will provide 24-hour protection in four shifts, on a 20-day rotation cycle per team.

Command posts will be set up as close as possible to the candidates' homes, which will be guarded whether anyone is there or not. Each candidate will be accompanied by agents while traveling, and will move about on the ground only in mini-motorcades. The federal government pays the Secret Service agents' salaries and expenses, but nothing more.

Each candidate will be assigned a Secret Service code name, primarily for use in radio communication between bodyguards.

In 1976, for example, Dole's code name was "Ramrod," and his wife, now Transportation Secretary Elizabeth Hanford Dole, was referred to as "Rainbow."

The senator probably won't have the same code name this time, and neither his wife nor the Democratic candidate who might like the code name, Jesse L. Jackson, will be designated "Rainbow." That's because the moniker has been assigned to first lady Nancy Reagan. Jackson was known as "Thunder" in the 1984 campaign, while Vice President Bush's code name is "Timberwolf."