THEY SOMETIMES call it the "rule of three," and it finds its way into lots of newspaper and television reports. The rule assumes that three similar events constitute a full-fledged trend - and with it, a bunch of experts are rolled out to analyze and assess the thing to death.

Three plane crashes and everyone worries about safety. Three box office disasters and the studio head is suddenly history. Three interest rate hikes and a new recession is on the way. It's simply a way of categorizing stuff.So when a bullet of still unknown origin barely nudged the South Portico of the White House last week, trend-watchers were prepped. It had been the third "attack" on the White House over the past three months and though President Clinton was never in much jeopardy, the rule of three kicked into operation.

As it turned out, there would be a fourth incident: A knife-wielding homeless man was shot Tuesday morning by a Park Police officer - right in front of the White House. He died the next day.

Beyond any immediate concerns about the president's safety is a long-range question: Is there something about this particular president that makes him especially vulnerable to the armed and festering crazies? Four separate events must mean something, right?

Well, clearly he is an unpopular guy and for all the well-established reasons, from the underlying influence of Hillary, to the barnstorming invective of Rush Limbaugh, to his own moral lapses, which are too obvious and numerous to blame on someone else's agenda. This is more than just a political problem; Clinton's woes have become so ingrained that you'll find them being crudely played out in joke books and greeting cards (middle-aged gut included).

The upshot is that a substantial and vocal minority not only disagrees with the Clinton agenda, but has a deep-seated dislike of the man himself. That is made clear in a U.S. News & World Report survey showing that 20 percent of the respondents fall into the category of "Clinton haters" and 25 percent simply don't like him.

Perhaps that's why North Carolina Sen. Jesse Helms' off-handed and small-minded suggestion that Clinton "better have a bodyguard" if he visits the state carried so much firepower. Helms was only saying what lots of voters were thinking.

Outgoing administration aide David Gergen correctly describes the electorate as angry and looking for scapegoats. "It's a free-floating kind of resentment that may attach itself to . . . all sorts of forces and I think it has attached itself to a very large degree to President Clinton," he said.

But trend-tracking these matters can get complicated - sometimes, positively contrary.

How else to explain the increasing number of death threats being received by incoming House Speaker Newt Gingrich? The Georgia representative, who arguably has injected more anti-Clinton venom than anyone, must now get round-the-clock protection. So, too, must numerous federal officials (and actors, sports stars, models and executives).

As for the knife-wielding Marcelino Corniel, he may have had a grudge against Clinton, but it was probably no larger than the rootless grudges he had against other officials and institutions. Those bullets that landed on the White House steps may have been intentionally aimed at the executive mansion, but there's no actual evidence of that. A Colorado man accused of firing 20 shots at the White House last October may have had it in for the president, but it could well have been any president.

The point is stuff happens these days - whether you're president of the United States or of the local PTA. "What it proves," said White House chief of staff Leon Panetta when asked about last week's mystery shots, "is we are living at a time when incidents of violence take place not just in cities and communities around the country, but also here in Washington in front of the White House."

That's an oversimplified explanation for what's been happening at or near 1600 Pennsylvania Ave. - though so is the conclusion that Bill Clinton alone is some kind of moving target. These are angry, unhappy times, and those in power - not just the president - have become lightning rods for those feelings. It's as simple and as complicated as that.