Senate Finance Committee Chairman Sen. Max Baucus, Monday, Dec. 14, 2009, in Washington. (AP Photo/Haraz N. Ghanbari)

The moment of decision on health-care reform is arriving for progressives in Congress. Some of them have insisted they will refuse to vote for any bill without a public option, and that is now the only bill that has any chance of passing. If they hold to their position, the most significant social reform on behalf of low-income Americans in 40 years will go down to defeat.

It should hardly be surprising that we have come to this point. The requirement for 60 votes in the Senate to pass ordinary legislation was always going to empower the most conservative members of the Democratic caucus or the few moderate Republicans who might support...