Congressional districts are supposed to allow equitable representation. The total popular vote is useful for determining whether the representation is fair. If districts are drawn correctly then the percentage of popular vote a political party wins should be should be close to percentage of representatives elected for that party. The closer the difference between the popular vote split and the representative split, the fairer the election.
If the difference between the two tallies is off by more than 33%, then there is something fundamentally broken. It allows candidates to spew extremist views, because they won't be challenged in their home district.
