Textfield returning two values simultaneously?

I'm trying to design a password system for loading levels, similar to Metroid. I'm using a Text Field to get the user's input, then comparing that input against a list of preset passwords when the user clicks a submit button. The issue is that the input being sent to the comparison is always an empty string.

When I put a Log call in OnGUI it looks like it is returning two frames of an empty string, and then one frame of whatever was actually in the field.

Code:

 void submit(){
     Debug.Log("Method call: " + password);
     Application.LoadLevel(checkPassword(password));
 }

 int checkPassword(string passwordToCheck){
     Debug.Log("String check: " + passwordToCheck);
     int levelToLoad = 0;
     switch (passwordToCheck){
     case "Password1":
         levelToLoad = 1;
         break;
     case "Password2":
         levelToLoad = 2;
         break;
     ...
     }
     Debug.Log(levelToLoad);
     return levelToLoad;
 }

 void OnGUI(){
     password = GUI.TextField (new Rect(Screen.width / 2 - 75, Screen.height / 2 - 38, 150, 75), password);
     Debug.Log("From OnGUI: " + password); 
 }