There were 60 Democrats in the Senate on Christmas Eve 2009, when they voted in lockstep to pass the Affordable Care Act. Soon there will be 46 Democrats in the Senate, or perhaps 47, if Sen. Mary Landrieu manages to eke out a win in Louisiana. In plain numbers, the post-Obamacare trajectory has not been good for Senate Democrats.

The 46 or 47 Democrats in the next Senate are a bit different from the group that passed Obamacare. Sixteen of them took office after the Affordable Care Act was signed into law. They never had to vote for it and have never had to defend voting for it.