Republican senators have blocked legislation that would trim payments to private health insurers serving people in Medicare and use the savings to raise reimbursement rates for doctors. Democratic leaders in the Senate tried to advance a bill costing $19.8 billion over five years and paid for mainly by phasing out some payments to insurers. Payments rates are set to drop by 10.6% on July 1 as a result of a formula that calls for cuts when spending exceeds established goals.