Total spending on this year's Congressional elections will likely top $3.9 billion, according to a new projection from the invaluable Center for Responsive Politics. This would make 2014 the most expensive Congressional election cycle in history, easily topping the $3.6 billion spent in 2010 and 2012:
The midterms as a whole will likely cost considerably more. This figure doesn't count any of the contested governors' races around the country. And for Congressional races, it leaves out spending by outside groups on "issue ads" that don't have to be reported to the FEC.
Based on what has been disclosed, the Center estimates that $896 million will be spent by outside groups on Congressional races — but that there's probably at least $100 million more unreported. Head over to OpenSecrets.org for the full analysis.