WASHINGTON — The Senate has voted to spare plaintiffs' lawyers in medical malpractice cases from a cut in fees. By a vote of 32-66, the Senate rejected an amendment by Sen. John Ensign, R-Nev., to cap the fees that plaintiffs' lawyers can collect when they win a case. Ensign would have limited the lawyers to one-third of the first $150,000, and one-fourth of additional amounts above that. Democrats said the amendment was one-sided because it would not limit fees for defense lawyers in malpractice cases.