Uniform Swing

In 2008, Barack Obama defeated John McCain by 53%-46%. If Mitt Romney beats Barack Obama by 1%, he'll have improved on John McCain by 8%. The uniform swing theory of elections is that the national popular vote swing would be constant across all states. In 2004, George W. Bush improved on his 2000 two-party performance by 1.5%. Thirty of the 51 states/DC swung within 2% of that 1.5%. They moved between 3.5% toward Bush and 0.5% toward Kerry. Forty of the 51 were within 3%.

The uniform swing tab in this spreadsheet has the states moving within 2% of the Bush-Kerry move in light blue and those within 3% in purple. In 2008, 26 states were within 2 points and 35 were within 3. Among the states that weren't were Massachusetts, Arizona, and Hawaii, states that were the home states for John Kerry, John McCain, and Barack Obama.

While using uniform swing is acceptable for projecting 2012, but we should keep in mind that 10-15 states will be more than 3 points outside of it. While Obama improved 4.7% over John Kerry, John McCain actually equalled or improved on George W. Bush in 5 states. If Mitt Romney gets more popular votes than Barack Obama and improves on John McCain by 7 points or more, he'll probably improve on 2008 in no more than 1-2 states and might not improve in any.