Many physicians said to prefer single-payer system

Dr. Keith Paredes has seen it more times than he’d care to recall: A woman, bleeding heavily, comes to the ER. She needs an urgent surgical procedure, maybe even a blood transfusion, from a condition like untreated fibroids. She’s there because she hasn’t had a routine doctor visit for ages.

There are many reasons people put off going to the doctor. One of the big reasons is cost — a huge arc in the current debate about whether and how to repeal and replace Obamacare, which sought to increase the number of Americans with quality health insurance. Another is access, or finding a doctor who take...