Can Obamacare Be Changed To Make It a Single-Payer Health Plan?

Is it possible to change the Affordable Care Act into Universal Health Care?
Wouldn't Congressional Republicans block any such attempt to change the ACA?
The answer is... "Of course they would!"
But, if it ever got to that point...if President Obama and Congressional Democrats pushed for such changes, and the Republicans then blocked it, wouldn't the Democrats running for House and Senate seats in November be able to say:

"See,we tried to change Obamacare in a bi-partisan way to make it a better health care plan; but the Republicans refused to go along with us.
We tried to give the American people the kind of universal health care that nearly all the Western countries already have; but the Republicans said 'No'
We are for the American people.
The Republicans are for the big insurance companies."


Sanders Subcommittee Hearing-Access and Cost:What the US Health Care System Can Learn
http://www.democraticunderground.com/10024655434/

Single-Payer Advocates: It Hurts To Say I Told You So
"We may have an 'I-told-you-so' moment, but it's hard to get any pleasure out of it knowing how many people are actually going to get hurt," said Stephanie Woolhandler, a New York-based doctor who co-founded Physicians for a National Health Program, a group that pushes for universal health care..."You had a bad system, and you're putting a patch on it using the same flawed insurance companies that got us here in the first place," she said.
http://www.huffingtonpost.com/2013/11/22/obamacare-single-payer_n_4312394.html/

Physicians for a National Health Program:
http://www.pnhp.org/


Poll: 64% of Americans Say Obamacare Should Remain Law
"Bloomberg News found that a combined 64% of Americans said they support keeping the law in place..That includes 51% who said it should be kept, but may need some small changes."
http://www.democraticunderground.com/1014754006/

(Note that 51 percent said that the law "may need some small changes"...I wonder how many would have said that Obamacare should be changed to make it a single-payer health plan, if that had been an option for them to choose?)