Removing text styles

[Jim Hurley]

When I run the following handler, the style of the text is not plain. 
It retains the text shift.

on mouseUp

   put "Now is the time." into field 1
   set the textshift of char 3 in  field 1 to 3
   set the textstyle of char 1 to -1 of field 1 to "plain"

end mouseUp

However, if I select the text and, from the Text Menu, select "Plain 
Text", the style does indeed revert to Plain text.

I would have expected the menu action to be the same as the command 
line in the handler.

How would one remove the textshift of a field programmatically?

Jim