They are not trying to save the Post Office, they want to kill it. If you remember, it was the Republicans in 2006 that passed a "reform" bill that forces the Post Office to put $5 billion a year into a pension fund to pay for pensions 75 years into the future. They want the fund filled within a 10 year period. The Post Office already has a pension fund and other worker funded retirement plans. The Republicans created the problem, and now they are using the shortfall as reason for attacking the Post Office.
Post Office jobs are good paying middle class jobs. If the Republicans succeed in killing the post office, hundreds of thousands of jobs would be lost, including businesses that depend on the Post Office and the buying power of postal workers. It would also hurt UPS and FedEX. They use the Post Office for the last mile in regions they find unprofitable.