For a long time now, progressives have been looking for lines in the sand. They’ve been trying to get progressive members of Congress to commit to vote no on any health care reform bill that doesn’t include a robust public option, and they’ve also been after the President to clearly state his unwillingness to sign a reform bill without one. Today, in his weekly radio address, and framed by his characteristic eloquence, the President has offered not one but a number of lines in the sand.