The number of representatives a state has in the House has a direct bearing on the number of votes a state has in the Electoral College. Following apportionment, states that voted for Barack Obama for president in 2008 lost six seats in Congress and hence six electoral votes, while states that voted for John McCain gained six.
Also, depending on who moves into a state, reapportionment may signal a shift in a state's overall political hue – for example, from relatively blue (Democratic) to relatively red (Republican). Some states could shift into the "swing" category (purple). Others might move out of the swing category to more likely vote with one party or the other.
In very close elections (such as 2000), just one state shifting this way could change the outcome.
What's next?
The US Census Bureau soon will provide states with more detailed demographic data from the 2010 Census so that redistricting may begin.