Most of the advertising that irks Democrats was legal before Citizens United, and the plausible prospect of taking over one or both houses of Congress has energized Republicans, while Democrats are dispirited by the unpopularity of their party's policies.
Let's face it - it sucks to be a Democrat right now. For two years your party has had control of both houses of Congress AND the Presidency and while you've managed to ram through a lot of legislation, most of what you've done has been against the wishes of your employers - the American electorate.
You only have yourselves to blame for your potentially poor showing in the only Poll that counts - the one that will take place in November! Throw the bums out is the rallying cry of most Americans, Tea Party adherents or not.
And blaming George W. Bush for your predicament is the default position of whiney babies! You did your own silly selves in!