Sen. Bernie Sanders (I-Vt.) and former secretary of state Hillary Clinton agree that the U.S. needs universal health care -- but they disagree on how the government should be involved, and how the current system should be altered.  

Clinton wants to build on the existing system -- to use the infrastructure that Obamacare has created and improve it incrementally, adding new protections against out-of-pocket costs and getting moderately tougher with the prescription drugs.

Sanders, by contrast, wants to wipe away existing arrangements and create a single, government-run program that would insure everybody and provide far more generous coverage than exists today.

In an early debate exchange, Clinton explained why she favors this step-by-step approach. She thinks the Affordable Care Act achieved a great deal and, more important, she doesn’t want to start a whole new reform effort.

“I don't want us to start over again,” Clinton said. “I think that would be a great mistake, to once again plunge our country into a contentious debate about whether we should have and what kind of system we should have for health care.”

Sanders responded that it was unconscionable to leave people uninsured -- and that he thought the only path forward was to blow up the status quo and build something new, even if it takes a political revolution to do it.

“Every major country on earth, whether it's the U.K., whether it's France, whether it's Canada, has managed to provide health care to all people as a right, and they are spending significantly less per capita on health care than we are,” Sanders said. “So I do not accept the belief that the United States of America can't do that.”

Is Clinton too complacent about the way things are -- or too timid about seeking change? Could Sanders actually overcome the political resistance -- not just from special interests, but also from wary voters -- that his plan would provoke?

How you answer that probably says a lot about which candidate you support.