Vote as far left as possible all the way up, if it ends up as trump v clinton then it should be the lefter of the two.
And Democrats will always take advantage of that. They supported genocide last election. How much further to the right are they going to go? Because they will never move one Planck length to the left.
But if they consistently win it still alter the political landscape such that someone else will have a better chance on reenacting actual change in the future.
The two party system is garbage, but if one of the two current parties lost its ability to win entirely then a different second option could appear.
You can’t “push for more progressive options” when you’ve already ceded all power.
Democrats would not be expanding the concentration camps like the Republicans are.
History suggests otherwise.