This is a video of then-presidential candidate Barack Obama promising a crowd South Carolina that he'd walk a picket line if the right of workers to collectively bargain was being threatened—as is currently happening in Wisconsin:
"And understand this: If American workers are being denied their right to organize and collectively bargain when I'm in the White House, I'll put on a comfortable pair of shoes myself, I'll walk on that picket line with you as President of the United States of America. Because workers deserve to know that somebody is standing in their corner."
Look, if we spent all of our time getting really self-righteously mad when politicians break promises, we'd have very high blood pressure and probably be rather unpleasant to spend time with. But on the other hand, how great would it be to see President Obama walk a picket line? What is he even doing in Washington, right now? There's free pizza in Madison! He should bring an air mattress, though.