Presidential elections have always been a contact sport, but this year's promises to be particularly mean, dirty and hard-hitting.

It's all part of a day's work for sleuths, Democratic and Republican, who clinically call themselves "opposition research," but whose job is the muckraking and mudslinging in the presidential campaign. They uncover, catalog and computerize the words and weaknesses that lurk as potential targets in an opponent's personal and professional closets."I like to think of it (campaigning) in terms of people painting on a picture. Your opponent is coming over with a graffiti spray can," one Democratic campaign strategist explained.

President Bush recently ordered Republican campaign operatives to "stay out of the sleaze" business. But what's clear is that one candidate's sleaze is another candidate's substance. And this year the political sleuthing for Republicans will profit from new and pricey optical disk technology that makes research even more state-of-the-art. Democrats acknowledge there is a high-tech gap between the two parties.

Republican researchers have shifted resources away from Bill Clinton and are furiously playing catch-up on Ross Perot. Abortion, gun control and Social Security are the wedge issues they hope to drive against the Texas populist.

Clinton and the Democrats, who would like to leave most of the Ross Perot-bashing to Bush, believe they can turn the first family into the first target over alleged financial wrongdoing by some members.

("I hate the mudwrestling in politics. I think it's obscene") Perot delivered a below-the-belt shot to Bush recently by suggesting he started the Persian Gulf war to prove his masculinity. He said that as president he "would not send people onto the battlefield unless the nation is committed," and that he wouldn't have "to prove my manhood by sending anyone to war."

Perot also recently hinted he was more courageous than Bush for daring to come to Little Rock, Ark., and mingle with a crowd of supporters without bodyguards.

For now, Democratic strategists told us that Clinton has to spend his time defining himself rather than attacking Bush or Perot. Democrats are haunted by the Willie Horton specter and determined never again to allow their candidate to get hogtied by negative advertising. Democrats are approaching this election nursing a big grudge from 1988. Some fund-raising events have even been earmarked for intelligence-gathering on the opposition to avoid a repeat of 1988 when Michael Dukakis seemed tongue-tied.

A taste of the fall campaign is foretold in at least one memo prepared by the Democratic National Committee that calls for playing hardball on alleged ethics lapses in the first family. Some party officials want to see the national campaign take a page from the "in-your-face" style employed by Harris Wofford against Dick Thornburgh in the Pennsylvania Senate election.

The opportunity is to hammer the theme of "family favoritism" that would include a laundry list of sins, proven and unproven, against Bush family members, particularly son Neil. But officials also believe they can effectively mine the Quayle Council on Competitiveness to demonstrate a correlation between large campaign contributors and White House intervention in environmental and consumer protection rules.

By the time the votes are counted next November, Bush's 1988 Willie Horton ads may seem genteel by comparison.