Sanders faces attacks from many Democrats who think his steadfast dedication to ending inequality and his withering and relentless attacks on Wall Street are the machinations of a naïve idealist. For these critics, Clinton is the only choice because she’s all but locked up the election and has a “realistic” political agenda.

The thing is, such assumptions ignore everything that happened a week ago Saturday. These victories say something: that huge numbers of Americans believe Sanders should be president, and that his message — that inequality is unacceptable and government must do better for all of its citizens — is politically viable. They tell us that idealist politics are not naïve. They are valuable, they are popular and, most importantly, they are possible. (When actress Susan Sarandon set the Internet ablaze on Monday by saying that she might not vote for Clinton if Sanders fails to win the nomination, this is more or less where she was coming from, as she later made clear.)