WASHINGTON (AP) — Elizabeth Warren on Friday proposed $20 trillion in federal spending over the next decade to provide health care to every American without raising taxes on the middle class, a politically risky effort that pits the goal of universal coverage against skepticism of government-run health care.

The details of Warren's "Medicare for All" plan aim to quell criticism that the Massachusetts Democrat and presidential candidate has been vague about how she would pay for her sweeping proposal. Her refusal to say until now whether she would impose new taxes on the middle class, as fellow...