TMPro text changing script not working as expected

I'm new the C# Coding in Unity. Could someone point me to the reason why version 1 of the follow code works, but version 2 doesn't, when they should be the same?

I have a script that changes the text of a textmeshpro text. qBox is a gameobject I put into the editor, this is not changed between the scripts.

V1:

Code (CSharp):

1. void ChangeText() //Changes text.
2.     {
3.         TextMeshProUGUI mText = qBox.GetComponent<TextMeshProUGUI>();    
4.         mText.text = Scenarios.Scenarios[Scenario1Tracker.sNum,Scenario1Tracker.qNum].qText;    
5.     }

V2:

Code (CSharp):

1. void ChangeText() //Changes text.
2.     {
3.         string mText = qBox.GetComponent<TextMeshProUGUI>().text;    
4.         mText = Scenarios.Scenarios[Scenario1Tracker.sNum,Scenario1Tracker.qNum].qText;    
5.     }

The two should be the same, but the first works and if I change it to the second, it stops working. If I undo the changes, it works again. I don't get any errors in the Unity Editor or in Visual Studios.

Thanks in advance.