Andrew S. Rappaport says it will kill the claim of a natural Democratic majority:

Continuing to wallow in nostalgia and trying to reassemble the New Deal coalition relegates Democrats to long-term minority status. “If there’s a silver lining [in Kerry’s defeat], it is that it’s going to eliminate the ability [of Democrats] to argue that we have a natural majority on our side,” says California venture capitalist Andrew S. Rappaport, a leading funder of Democratic causes. “We don’t. It’s over.”