Mike the Mad Biologist asserts that Clinton's insurance mandates are "political suicide". (And he's correct, Clinton does not have the will or the political capital to stand up against the big insurers. No one does.) It is perhaps political suicide to propose any substantive, systemic changes to our health-care economics.
Since the current system — bad as it is — is actually in place, any actual change will inconvenience someone, and those inconvenienced will, naturally (and justly), complain. Someone's ox will be gored.
The nice thing, from a political perspective, about Obama's "plan" is that it's so obviously implausible that if he were elected, he'll suffer less political damage when no substantive changes are actually effected. (In just the same way, Clinton is in the Iraq war up to her eyeballs. She'll suffer less political damage when, if she were elected, she fails to end the war.)
Clinton's plan is the only workable plan that's on the table. If we do want to make substantive changes to health-care economics, the only alternative to mandated insurance (which is effectively a tax by virtue of it being mandated) is supporting the health care system through conventional taxes, which would also political suicide. And the same political and macroeconomic arguments would be marshaled against conventional taxation. For instance, a $200/employee/month tax on businesses would have almost exactly the same macroeconomic effects as requiring all working people to purchase $200/month of insurance. (The only difference would be that my employer would have more direct decision-making power over specific health-care choices.)
I'm generally against over-thinking in politics. If progressives oppose Clinton because her plan is seen to be "political suicide", it is we who are committing suicide. We are voting against our own material interests, and if we vote against ourselves, who will vote for us?
There are some battles it's better to fight and lose than refuse to fight. Clinton, Obama and the Democratic party would definitely be in a better position today if they had fought against the Iraq war, even knowing they would lose. Health care is one of those battles. Even if we lose, even if we know we're going to lose, we have to fight it.