In November 2008 Barack Obama won 53% of the popular vote in the state of Virginia. Twelve months later, the Democratic gubernatorial candidate there won 41% of the popular vote, 12 percentage points less. Obama won 57% of the vote in New Jersey, one year before incumbent Democratic governor Jon Corzine won 45%, also a 12-point difference. In Massachusetts Obama won 62% of the vote. Martha Coakely appears likely to wind up with 47% of the vote in today's special senatorial election, a drop of 15 percentage points.
One way of connecting those three dots is to say that any Democrat running for senator this year in a state that Obama carried with less than, say, 56% of the vote is likely to have an interesting election. Sen. Byron Dorgan of North Dakota, which gave Obama 45% of the vote in 2008, has already decided to spend more time with his family. Sen. Blanche Lincoln of Arkansas, which gave Obama 39% of its vote, has one of the most difficult challenges facing any incumbent in 2010.
Among the states Obama did carry, but not overwhelmingly, are these:
If the pattern in New Jersey, Virginia and Massachusetts holds that would be five Republican holds and four Republican gains.