diff --git a/packaging/_tokenizer.py b/packaging/_tokenizer.py
index de389cb3..17a47a11 100644
--- a/packaging/_tokenizer.py
+++ b/packaging/_tokenizer.py
@@ -35,7 +35,6 @@ def __str__(self) -> str:
 
 
 DEFAULT_RULES: "Dict[str, Union[str, re.Pattern[str]]]" = {
-    "LPAREN": r"\s*\(",
     "LEFT_PARENTHESIS": r"\(",
     "RIGHT_PARENTHESIS": r"\)",
     "LEFT_BRACKET": r"\[",