It's a perception thing, xo. Not whether sirs would have voted for her, but how others may have. When she looks so uncomfortable, answering so simple a question, that everyone in their right mind knows what the answer is, she comes across as "lacking". The very voter she may have been hopeful to get, tunes her out, as she looks like any other squishy politician, and the democrat base that would vote for her become disinterested in her apparent lack conviction/support for their guy
It's like when Obama goes to play golf right after he announces that ISIS has beheaded an American. It doesn't look good. In fact, its inappropriate, and condescending