Votes for demcrats are motivated by Hope, votes for Republicans are motivted by Fear.  The Corruption scandles only reduce votes for Repulicans (out of shame) but without Hope for improvement, does nothing to increase votes for Democrats.  

Politics corrupts all who touch it, the feeling goes, so really, it doesn't make much different who wins...

It's much easier to make people be afraid then it is to make them feel hopeful, but that's what Democrats need to do to win a landslide...really that's what clinton did, by talking about how politics works well, how it is an expression of our will in a positive way...how both democrats and republicans are parts of a system that is meant for Good.  

It isn't ideas that matter, it's just the idea that there is something to look forward too.  

A feel good ad campaing might do the trick.