Even if President Sanders is way out in left field, he can't pass laws. He can make executive orders, but to make real permanent changes he would need a congress full of little Bernies. He won't get that. Far from it. But what he can do is to sign every bill a Democratic congress sends him. So his "promises" are simply things he would like to do. Nobody is going to blame him if congress doesn't go along.

In particular, the House has to originate every bill that spends taxpayer money. And House Democrats are going to be just that: Democrats, not Socialists.