I'm of two minds on pragmatic politics. I agree that if you always vote for the lesser evil, the best you'll ever get is the lesser evil. I also agree that voting for a third party in a two-party system is like going unarmed to a gunfight. Working pragmatically in US politics means calling each shot on its merits. Most of the time, I vote for third-party candidates because that's the only way to register a protest, and I'm delighted when a third-party candidate like Kshama Sawant manages to get into a position where she may someday be able to make major changes. Right now, the only socialist we've got on the national level is Bernie Sanders, and until a purist socialist can point me toward a socialist who could have a greater effect on US politics this year, I will support him.
I'll add that I'm still enough of an idealist to think there's a tiny chance he can defeat the Clinton machine. It's not the smart bet, but it's worth supporting. If he's elected, I'll happily criticize him from his left. But until Clinton steamrollers him or he's elected, I'm not going to waste time on his shortcomings. I'll acknowledge what he's doing right, because that broadens the political discourse in the US, and that benefits the people who've always been my concern, the people of all hues and beliefs who keep getting poorer while the rich of all hues and beliefs keep getting richer.