The Edwards campaign has been pushing claims of electability for the last several months, most likely to distract potential supporters from his actual weakness in this area. Convincing supporters of the validity of this argument has been one of the few successes of the struggling Edwards campaign. For example, MyDD has a front page story arguing that John Edwards will help us with rural voters.
Before his decision to accept matching funds, along with the spending limitations this requires, there might have been some truth to this. Edwards might have done better than Obama in rural areas and possibly would have done better than Clinton, but his advantages in Iowa are fading. Edwards was also unable to help the ticket in 2004, even in his home state where he was considered to be unable to win reelection to the Senate if he ran.
Even if Edwards could have done better in rural areas with a level playing field, limitations on his spending now make it virtually impossible for him to be competitive in traditionally Republican areas. Republicans would be able to outspend Edwards by such a wide margin for several months that by the time of the conventions few in traditionally Republican leaning areas would consider him.
The other problem is that, while Edwards might have helped in rural areas if not for his limitations on spending, he would lose votes among far more groups. Edwards alienates independents, suburbanites, the “Starbucks Republicans” who voted Democratic in 2006, professionals (other than fellow lawyers), and more educated voters. His conservative record on civil liberties issues, social issues, and foreign policy, as well as his populist economic policies, are all negatives among such groups. The net effect of an Edwards nomination might be to pick up a few more votes in rural areas but it would not be worth the cost of alienating all those who are voting Democratic for the first time in decades.