Use PLY to match a normal string

I am writing a parser by using PLY. The question is similar to this one How to write a regular expression to match a string literal where the escape is a doubling of the quote character?. However, I use double-quote to open and close a string. For example:

"I do not know what \"A\" is"

I define the normal string lexer as:

t_NORMSTRING = r'"([^"\n]|(\\"))*"$'

and I have another lexer for a variable:

def t_VAR(t):
   r'[a-zA-Z_][a-zA-Z_0-9]*'

The problem is my lexer doesn't recognize "I do not know what \"A\" is" as a NORMSTRING token. It returns the error

Illegal character '"' at 1
Syntax error at 'LexToken(VAR,'do',10,210)'

Please let me know why it is not correct.