It's the word "credible" that is the key. You guys lost your credibility a long time ago,
And above and beyond that, this shows that the Dems both refuse to move away from both the notion that there is free health care out there if they just try hard enough, and refuse to let go the notion that a command-and-control economy is the desired end objective, with the numerous documented failures of such economies not ever factoring in to their worldview. Which is a key reason they are losing - more and more people look at them and say "when in the hell are you going to allow reality and past experience to impact your political views?"
"Democratic congressmen can do that, for example, by making a credible collective pledge that if you vote Democrat enough you will never pay another medical bill as long as you live."
I guess economic illiterates will believe this. The rest of us understand that we will have to pay for the medical costs... PLUS 'handling charges' for the govt agency that oversees the bureaucracy. Not to mention the loss of time (and perhaps even LIFE) that comes with the govt being in charge of rationing health care. As someone in England just said, after the govt there lost a lawsuit on the subject, "Guarantee to health care should not be just a guarantee to wait in line."
You don't have to look as far as England, or even Canada, to see what a wreck 'free' health care is. Just ask, "Do you REALLY want your doctor's office to look like the DMV?" That usually brings anyone around to a true understanding of the true costs of 'free' health care.
The fastest way to shutdown collective health care is to move to a flat tax; until everyone is paying a share of the government's costs, politicians will continue to sell 'free' IMHO