The argument put forth by many Sanders supporters is to start off with the ideal and then negotiate down. The point Wetzilla is making is that many of the progressive ideals are unthinkable for the Republicans in Congress.

If Sanders starts off demanding a monumental overhaul of the healthcare system to a governmental single-payer healthcare, the Republicans won't even bother negotiating. They will walk away and you will end up with nothing. If Sanders demands a tax on Wall Street transactions to fund national college tuition at state run universities/colleges, Republicans won't bother negotiating because it's antithetical to their belief in smaller government (on two fronts, both the tax and the tuition).

If you don't believe that the Republicans will walk away from the table, then you need to look at the past 6 years of what Congress has accomplished. The only reason the ACA passed is because of the majority the Democrats had, and it was watered down even with all that support.

There has been a lot of talk about how FDR gave the New Deal, how LBJ accomplished the Voting Rights Act, and how JFK got America to the moon. What people aren't remembering is that:

• FDR had a supermajority in both the House and the Senate with the 73rd, 74th, and 75th Congresses.

• JFK had a supermajority in the House and the Senate during his entire presidency with the 87th and 88th Congresses.

• LBJ had a supermajority in the Senate and a near supermajority in the House when he took over after JFK was assassinated for the 88th and a supermajority in both the House and Senate during the 89th Congresses.

The point I'm trying to make is, sure it's great to dream big, but it takes a ton of support to get monumental change to happen. The FDR, LBJ, and JFK all got major policies enacted, but it was because they had people in Congress willing to work with them.