Commenter MC offers this thought:

Another wrinkle that a lot of people leave out is that many of us have, and more of us should have, a bias towards the status quo on any issue. It's a bias that can be overcome if the people advocating change make a really good case, but we place the burden of proof squarely on those who want to change something. If they don't make a good case for the specific change they propose, the other side isn't obliged to do anything. But of course the other side can make a case for a different change, if they want to, in which case the burden is on them.

Note that this isn't to say the status quo is perfect. It's just that we have full information about it, because the experiment has been run and the outcome is there for all to see. We can see the good points and the bad. But with any hypothetical change, we really don't know what is going to happen. The benefits that proponents of the change promise may occur, or they may not. There will almost certainly be unintended consequences. We don't really know. And that suggests a need to move slowly, test things out, communicate honestly about what does and does not seem to work, and so forth. The exact opposite of bumper sticker politics and rushing through legislation before the public can digest it and weigh in.

The Democrats have failed the communication test rather spectacularly in this case. And a lot of people who are NOT stupid or uninformed can articulate real problems with the bills Congress has passed. And so, for these people, the Democrats haven't met the burden of proof and we should default to the status quo for a few more years.

This isn't about a preference for public vs. private sector solutions either. I would apply the same kind test to a proposed change that involved privatizing something the government currently does. The lack of information is the same no matter which way you are going.

It's a dynamic neither side pays enough attention to.  It brought down Social Security reform, and it looks now as if it may have brought health care reform down too.