D
Deleted member 231381
Unconfirmed Member
As said above:
The trouble is that this ignores the very next step of governance. The fact that Sanders is there and you voted for him does not mean you will get his platform: The Socialists and Democrats of your example would then need to form a coalition to actually govern properly and pass policy.
Yes, of course. I don't get his platform; I get an element of his platform, presumably proportional to how many seats he commands in the legislature and therefore the capacity to influence a winning coalition. However, you seem to think that US coalitions form, even prior to elections. They don't, not really. Clinton doesn't have to adopt any of Sanders' platform or compromise in the slightest, other than is necessary for him to bring voters to her. Even then, there's commitment problem; once in office, the president is unassailable, and they have no real incentive to honour their coalition, especially given the incumbency bias. In a parliamentary coalition, if you aren't response to a coalition partner, then they withdraw support and you lose office, so you are necessarily responsive to a broader spectrum.
There's a fair amount of comparative government study on this. It's the main reason why official UN advice for the constitutions of newly governed countries is not to use presidential systems. There's a very strong relationship between the stability of democracy and presidential/parliamentary executive type, for example, in post-colonial Africa. The United States is actually the only presidential country never to have been a dictatorship at least once.