Somethings get alluded to over and over but never actually explained:
Democrats will lose control of Congress if they don't pass a HealthCare bill.
I think they know this but just in case you don't, here's why:
Republicans are vigorously opposing anything Democrats and the President do. Sometimes it is completely antagonistic, while other times it is "cherry-picking". For example, many Republicans both in office and regular voters might say they support forcing insurance companies not to drop paying customers because of "pre-existing" conditions, but they oppose an individual mandate for Americans to be covered. While others may just demagogue, and be against "a government takeover of healthcare". Either way it is pretty easy to get nearly 100% Republican support against such a massive bill.
Independents are not firmly for or against this whole process and will follow the most convincing and usually most intense side of the debate. A rule in politics is that it is easy to scare someone than to excite them. So it is easier to get an indepedent to vote against someone who is threatening their lifestyle rather than tell them that what you are doing will help them in the long-run. Even if what you are doing will help, a critic can always find something that is detrimental and make that the most important part for that person. So there will be a tendency to go against the Democrats on this.
Then if Democrats get depressed that, even with 60 votes and a new President, "we still can't get healthcare", "what's the point of voting Democratic", then similar to 1994 there will be a dip in left leaning voters.
Add to all of this the natural tendencies toward divided government, and the natural political cycles that general punish the party of the newly elected President in the next off-year election and Demcrats should get the message:
Pass a good health care bill. The best one you can think of. It may be your last chance for generation.
If you do a good job, you will minimize the drop off on our side in terms of turnout, and may actually convince indepedent voters to stay the course.
Anything else may be a disaster.