Democrats have been saying that once health care reform takes effect, it will be harder for opponents to spread misinformation about its contents. Brendan Nyhan has a New York Times op-ed pointing out that this hope is probably too optimistic. Nyhan has done research on political misperceptions, and found that partisans are highly resistant to correcting mistaken beliefs that confirm their ideological predilections. In a 2006 study, he found that liberals are just as likely to believe that President Bush imposed a complete ban on stem cell research, private as well as public, even after being exposed to information informing them that this is not true.
More disturbingly, conservatives are not only immune to such corrections, the corrections actually backfire. Informing them that there were no weapons of mass destruction found in Iraq, or that Bush's tax cuts did not cause federal tax revenues to rise, actually cause conservatives to believe these things more strongly. (In other words, posts like this are probably backfiring. Oh well.)
So it's probably not very likely that even the actual implementation of health care reform will kill of misperceptions about it, especially if conservatives continue to disseminate them.
What I think will help Democrats, though, is simple status quo bias. People distrust Washington in general, and such distrust tends to run higher during times of economic stress. This puts an onus on whichever side is proposing change. Democrats have faced an uphill climb convincing the public to accept major changes to the health care system, and the Republicans have successfully focused much of the debate on the most vulnerable points of that proposal. But now that Republicans are the ones proposing to change the system, the status quo bias will operate against them Democrats can ask why they want to allow insurance companies to deny coverage to people with preexisting conditions, throw thirty million Americans off their coverage plans, and so on.
The status quo in American health care is easy to defend when you can make the debate a referendum on an alternative. But when you have to convince people to take positive action to restore that status quo -- or at least large elements of it -- then the onus shifts back.