ELECTIONS ’92 : Candidates Prepare for Last Debate : Countdown: Bush spends day at Camp David, Clinton wins new endorsements and Perot stays out of public eye.

ROMULUS, Mich. — With the last of their three debates scheduled for Monday, the three major presidential candidates spent Saturday largely in private preparations for their final direct confrontation before the Nov. 3 election.

President Bush spent the day at Camp David, the presidential retreat in Maryland’s Catoctin Mountains.

Democrat Bill Clinton traveled to Michigan--the site of the final debate--and in his one public appearance basked in endorsements from current and former prosecutors.

Independent candidate Ross Perot continued to refrain from any public appearances, but he aired an hourlong commercial on ABC Saturday night. The spot consisted of two parts--a repeat of a 30-minute program aired Friday in which he discussed his proposed solutions to the nation’s economic problems and a 30-minute biographical segment that focused on his Depression-era upbringing near the Texas-Arkansas border.

Clinton had two brief encounters with reporters Saturday--in Little Rock, Ark., where he began his day, and in Romulus, where he stopped before engaging in preparations for Monday’s debate in East Lansing, Mich.

With his aides saying that their polls--like those conducted for several news organizations--showed the Democratic presidential nominee’s lead holding steady, he was able to project with one word--”sad”--an air of scornfulness when asked about Bush’s angry put-down of hecklers on Friday and the President’s latest attack on Clinton’s draft record.

Campaigning in New Jersey, Bush called the hecklers “draft dodgers,” and said for the first time that his opponent had evaded the draft, rather than merely avoided it.

Clinton sought to counter the almost-cocky mood being projected by his staff. The Arkansas governor insisted that his plans to campaign this coming week in several Western states that have been solidly Republican in recent presidential campaigns should not be read as a sign of confidence in the election’s outcome.

And any talk of a landslide, he said, is “way premature.”

“The election is a long way from over; 17 days is a lifetime in public life,” he said.

Yet the Western swing, according to the Clinton campaign in California, will include a stop Thursday in Orange County, where Republicans rely on a heavy conservative turnout to help swing the state to GOP presidential candidates. A visit there by the Democratic candidate at this late date in the campaign would suggest an unusual degree of confidence.

Indeed, public opinion surveys have shown the presidential race in the county to be unusually close--dimming Bush’s chances to carry California and its 54 electoral votes, which represent one-fifth of the 270 needed to win election.

During his only public event of the day, Clinton was endorsed by a group of 33 state attorneys general--all of them Democrats--and by dozens of local prosecutors as he continued his battle with Bush for law-enforcement endorsements.

The President has been endorsed by several national police organizations and local police groups. The backing he received from the Fraternal Order of Police in Clinton’s hometown of Little Rock has become a centerpiece of his effort to challenge the Democrat’s effort to project a tough-on-crime image.

Joining in the Saturday endorsements of Clinton was Sarah Brady, the wife of Ronald Reagan’s press secretary, James Brady, who was gravely wounded in the assassination attempt on the then-President on March 30, 1981.

Clinton has endorsed the so-called “Brady bill,” a measure Mrs. Brady has pushed that would impose a five-day waiting period on the purchase of handguns. Bush has twice vetoed legislation containing the measure.

Today on the Trail . . .

Gov. Bill Clinton campaigns in Ypsilanti, Mich.

President Bush has no public events scheduled.

Ross Perot has no public events scheduled.