NY -- Standard&Poor's CreditWire 7/18/96 -- Standard&Poor's today has assigned its preliminary double-`A' rating to The St. Paul Companies Inc.'s $192.7 million Rule 415 senior debt securities shelf registration. Standard&Poor's expects financial leverage to remain in the 15%-20% range. The shelf is expected to be used for general corporate purposes and to enhance the company's short-term financial flexibility. MAJOR RATING FACTORS -- St. Paul Fire&Marine continues to maintain superior underwriting profitability despite the pressures on its medical malpractice segment. The combined ratio has remained at a favorable 102% for the last two years. -- The John Nuveen Co., The St. Paul's majority-owned investment management operation, continues to be a superior investment. In