Assume one predefined tag is needed

In tag fields, trigger the list view of tags only after clicking within the field.  If I need another tag, let me click the field again.  Currently, the behavior assumes that if I choose one tag, I'll probably want more.  I don't, but I have to click somewhere else to get the drop-down list to go away.  This forces me to find a safe area to click where I'm not going to trigger some other event.  Even if I could hit the Escape key to make the drop-down go away would be better.  (Yes, if I use the Tab key, the list goes away but I never "tab" through the forms in Aha!)  It just seems more intuitive to click-select then click-select again.  This one is hard to describe, so I hope you understand what I'm getting at.  The key is, don't assume that I always want to select multiple tags.  Interestingly, if I remove a tag, the list goes away.