HIALEAH'S executive mayor, Raul Martinez, has been managing that Northwest Dade city of 165,000 residents for eight years now. Because of his past refusal to quit dealing in real estate within the city, however, the last four years have been a sort of private hell for him. Mayor Martinez has been the subject of two Federal criminal investigations of zoning profiteering in Hialeah. Though both were fruitless, he now is being investigated anew by a Federal grand jury.

Mayor Martinez denies any wrongdoing. Nevertheless, he recently conceded to The Herald that his real-estate moonlighting undoubtedly has created the appearance of a possible conflict of interest. He now says that if he had it to do over again, he would refrain from outside employment. He should. He earns a $75,755-a-year salary as full-time mayor.

Despite the distractions of investigations that have not produced any evidence of wrongdoing, Mayor Martinez has managed to do much that's right. His administration recently won a hard- fought Federal-court suit against a santeria church's ritual animal sacrifices. It has also moved to revoke the occupational licenses of four motels in seedy areas, dismantled an alleged big-time drug ring, and designated the Hialeah Park racetrack a local historic site. Understandably, the mayor still enjoys widespread popular support. At the statewide level, too, Mayor Martinez has exhibited proven leadership qualities.

By contrast, his principal opponent, Nilo Juri, is most of all a political opportunist who's overeager to advance himself. Elected to the Florida House last year, he resigned that seat after less than one year in order to run for mayor.

As a result, Mr. Juri has little to show for his short- lived and undistinguished legislative career. Likewise, his mayoralty campaign at times is devoid of issues and instead resembles a single-minded personal assault on the incumbent.

With some reservations over the cloud that continues to hang over him, The Herald nonetheless recommends the re-election of Mayor RAUL MARTINEZ.