When she knows what she's talking about:

Look: she may get through this debate on Thursday. Biden may well help her. That's why I want a press conference to really find out what her actual expertise is. Only a robust give-and-take and follow-ups can prove anything. She can follow a script, she can repeat canned answers. We know that. What we need to find out is if she knows anything about national and international policy issues. Only a press conference will do that.