1. You have a plan that’s been vetted by the electorate.
2. You don’t have a messy and secret planning process to get attacked for months, letting opposition mobilize.
3. You have a President with an actual mandate, for himself and his plan.
4. You have a Democratic caucus that is capable of holding together.
5. You have the self-interested willingness of fringe Republicans to peel off.
2 is irrelevant. Clearly, in some sense the disagreement just hinges on 4 and 5 — obviously if all Democrats plus some Republicans are prepared to support dramatic health care reform, then dramatic health care reform is possible. I think all Republicans and some Democrats would welcome the existence of a dramatic health care reform proposal as an opportunity to demonstrate their value to their paymasters in the health care industry.
Thus, this winds up falling back on 1 and 3 — the idea that the existence of a mandate for change is likely to alter the voting preferences of legislators. I know that a lot of people find this hard to believe, but as best I know very few political scientists or other scholars of American political institutions believe that this is actually how things work.
Last, I’d note one other thing that’s changed since 1993. Back in 1993, opposing a popular Democratic health care plan must have struck GOP legislators as kind of risky and a bit crazy — a young gun kind of notion coming from Bill Kristol and Newt Gingrich at odds with conventional thinking and the views of other party elders. Now, the GOP has, among other things, the example of 1993 to fall back on — evidence that successful congressional obstruction will be politically helpful to the obstructors even if the obstructed policy is a popular one.