Years before the killing of Kate Steinle in San Francisco, sanctuary cities were a hot issue in the 2008 Democratic presidential primary campaign. And as it happened, the three top figures in today’s Democratic party — Barack Obama, Joe Biden and Hillary Clinton — were all running for president and were all grilled, in a single debate, about their stands on the question.

Only one — Biden — said he would not allow cities to defy federal immigration law. Obama sidestepped the question but managed to leave the clear impression he would allow sanctuary cities to continue. And Clinton made clear she would leave sanctuary cities untouched.