WITHIN the upper echelons of the Democratic Party now comes the new, and frequently expressed, hope that the Democrats may have finally found in the so-called ''sleaze factor'' an issue on which they could defeat the President.
These Democratic leaders believe that the accumulation of improper acts by those around the President is rubbing off on Mr. Reagan.
And they see in the most recent charges of inappropriate conduct by Attorney General-designate Edwin Meese III just what they have been looking for:
A highly publicized and therefore highly visible scrutiny of the ethics of a public servant who has been working at Mr. Reagan's side for years.
Further, Ed Meese, who became closely associated with Reagan when he was governor, is often referred to as one of the President's ''best friends.''
Also, because of Watergate there now is a public expectation - a demand - that the officeholder at all levels, and particularly in the presidency - come up to a higher level of ethical conduct, that he or she must meet the Eisenhower standard: ''Clean as a hound's tooth.''
A special prosecutor will look into financial help received by Meese from individuals who were later given federal jobs. He will also take a special interest in a $15,000 loan to Meese's wife not reported on his financial disclosure statement. Meese's position is that the loans and job appointments were coincidental and that the failure to report the one loan was ''inadvertent.''
Defenders of Meese say that much of his trouble today stems from his being less attentive to details than he should be. They also complain that opponents of the President are using the Meese case to get at Reagan.
But whatever his rationale, Mr. Meese should know that he will not get out from under this easily.
At most, some illegality may be found. But at the minimum Mr. Meese has already trod on shaky ground: He has forgotten that a public servant, particularly one close to the presidency, must not only avoid wrongdoing - he must avoid the appearance of wrongdoing.
But no matter what the disposition of the Meese case will be, the Democrats have yet to prove that they have come up with their much-sought-for issue for beating Reagan.
There is no evidence that a long succession of questionable conduct on the part of key administration people has yet darkened the image of the President - except in the eyes of his critics.
This could come. Meese has become an embarrassment to the President in a political year. But polls continue to show that public trust in Reagan still running high. As one Democratic leader confided: ''There's all this tawdry stuff going on around Reagan. But it somehow doesn't stick to him. If Carter were President, think how badly he would be tarred by now by all this ''sleaze.''
Reagan does stay above it all. Perhaps it is because he has a rather detached , delegating way of dealing with his subordinates. In any event, in the public eye, it is almost as though there were two separate entities: 1, the President, and 2, his administration.
When asked about Meese's alleged misconduct, Reagan was able to brush the question off by saying he simply never inquired into his aides' personal activities.