The night's confrontations were mostly fought on familiar terrain for the Democrats, who have spent months sparring over the future of health care with former Vice President Joe Biden and other moderates pressing for a measured approach while Warren and Sen. Bernie Sanders call for a dramatic, government-funded overhaul of the insurance market. Still, unlike Sanders, Warren refused to say whether she would raise taxes on the middle class to pay for a Medicare for All universal health insurance plan — a stance that's increasingly difficult to maintain given her more prominent status.