How to preserve indentation in wordpress [sourcecode] tags

Dont use the visual editor. Copy the code into your 'HTML' view and it will preserve indentation. Copy it into 'Visual' view and your code will be all left-aligned...

Examples:

Code pasted in 'Visual' View

<indent>
  <indent>
    <indent> </indent>
  </indent>
</indent>

Code pasted in 'HTML' View

<indent>
  <indent>
    <indent> </indent>
  </indent>
</indent>

YMMV, but this is what works for me.