I'm an actuary for a life insurance company. My father is a health economist, and has been working on universal health care for some time. So I have a little experience on this issue.
I honestly don't know for whom I'm going to vote tomorrow in the Massachusetts primary. As stephdray wrote, Barack Obama offers the potential for a politically transformative moment in history, and it would great to be there when it happens. Hillary Clinton, on the other hand, possesses encyclopedic knowledge and extrodinary command of the issues. She also has experience taking those slings and arrows from Republicans, and sticking it to them when it comes time for policy debates. We know how mean and vindictive those Republicans can be, and Barack Obama does not have this critical experience of taking on those Republicans. Mario Cuomo is right: you campaign in poetry, and you govern in prose.
On health care, I, however, strongly agree with Hillary Clinton. As Partially Impartial explains in his diary this past Saturday, without a mandate, many young, healthy people like myself (I'm 28.), by having to subsidize the premiums of older, sicker, higher-risk people, would not see purchasing insurance as a good return for their investment, and would choose to opt out of the system until they saw themselves as having the potential for getting a good return for their investment (in the form of premiums) -- when they are sicker. The mandate, by requiring young, healthy, low-risk people to join the system and subsidize older, sicker, higher risk Americans, is what lowers the cost for everyone.
As a better example, just think of Social Security or Medicare Part A (the Hospital Insurance). Both programs are mandatory; everyone must contribute in the form of payroll taxes. Not everyone, however, benefits. If you aren't lucky enough to live to 65, or are unfortunate enough either to become disabled, or have a parent or spouse whose income you depend upon die prematurely, you don't get Social Security and/or Medicare benefits. That's just the way insurance works. Insurance isn't an investment policy; it's a policy to guard you against catastrophic losses.
Now imagine if, as Barry Goldwater proposed in 1964, payroll taxes (Social Security contributions) were made voluntary. You could opt out of the Social Security system. If you were a young, healthy 25-year-old, why would you want to pay Social Security taxes through your nose if you see very little possibility of benefiting from your contributions? Wouldn't you rather spend your money feeding your children or saving for that new home? Doesn't seem like Social Security is a good investment, does it? So then who would be left paying into Social Security? The people closer to retirement. Because a much smaller pool of people would be there to contribute to Social Security and Medicare Part A, there would have be either a much greater contribution rate or significantly reduced benefits.
So contrary to a fellow Kossack's claim, mandates are not a Republican thing -- they are a Democratic thing. Every single-payer proposal -- both the Conyers (H.R. 676) and the McDermott (H.R. 1200) proposals -- provides mandatory insurance. You can opt out of receiving benefits, but you can't opt out of paying payroll taxes (or your employer's payroll tax contributions through reduced wages).
Now would Hillary Clinton's mandate force people into private insurance plans? Yes, everyone would be forced to purchase private insurance, and everyone would be allowed to buy into the Federal Employee Health Benefits Program (FEHBP). In my previous life as an economist for the US Commerce Department, I had the Blue Cross/Blue Shield Standard Option of the Federal Employee (FEHBP) plan. Contrary to what many people say on this blog, the plan is actually quite nice. But here's the bigger thing: by allowing everyone to buy into FEHBP (as Obama's plan also does), people would be able to have their insurance independent of their work. That way, when people change jobs, they don't have to worry about what health insurance benefits they may have to lose.
I hope this diary clears up many of the misconceptions about the mandates debate.