Salomon Melgen, the Florida eye doctor whose relationship with Senate Foreign Relations Committee Chairman Robert Menendez, D-N.J., is now the subject of a grand jury investigation, has left a trail of lawsuits over bad investments, including one involving a government contract in which he had attempted to tie his money to the coattails of another prominent Hispanic official.

Melgen, who has a port security firm in the Dominican Republic that Menendez denies he tried to help and a medical practice in Florida that the senator admitted he aided, has filed numerous lawsuits over other business dealings that went sour ...