Republicans’ lock-step opposition to comprehensive health care reform seems to be as much a matter of politics as principle. But either way, they have made clear that there is no dialogue or any possible compromise that will persuade them to change their minds.

That means it’s up to Congressional Democrats to move legislation forward — or throw away a once-in-a-generation opportunity to fix this country’s broken health care system.

On Wednesday, President Obama called on Congress to quickly take an up-or-down vote. He and Democratic leaders in Congress are going to have to work overtime to corral skittish members of their caucus. And Mr. Obama is going to have to keep making the case to the American people that reform is essential for all Americans’ security and...