[EDIT] I note you also reference Krugman.
There was also one by Krugman who has been very critical of anything not liberal for years. He has been trying go get to govt paying for many things for years. Wants higher taxes, govt funded healthcare, higher safety nets, transfers to poor, etc. I used to respect him and thought him one of economic's brightest lights but he has seemed to become single-minded recently. As for his stance, he ignores impact of single payer on innovation and on rationing of treatments.
In the op-ed, he refers to paying for the new care mainly with savings. But also notice the comment about how most will pay no more than they do today - a veiled reference to a tax increase on the wealthy. As a hint to where he might want to go, he has been calling for repeal of the ceiling on SS taxes for a few years.
Jon