The algorithm is actually kind of odd::

  >>> " a b".split(None, 0)
  ['a b']
  >>> "a b ".split(None, 0)
  ['a b ']
  >>> "a b ".split(None, 1)
  ['a', 'b ']

So trailing whitespace on the original string is stripped only if the
number of splits is great enough to lead to a possible split past the
last element.  But leading whitespace is always removed.

Basically the algorithm stops looking for whitespace once it has
encountered maxsplit instances of contiguous whitespace plus leading
whitespace.