Where's all the money coming from?

Considering how the total election spending this year amounted to almost $4 billion, and Democrats alone spent $1.76 billion, there is a lot of questions as to where the money came from. This chart shows spending in past elections, along with a projected spending for the 2014 elections.

This also includes undisclosed spending, referred to as 'dark money'. Dark money is mostly donations from sources that aren't revealed to the public. 

A lot of Democratic money comes from President Obama's fundraising; he has done about 50 fundraisers this year to gain money for the midterm elections. This is an interesting turn, considering how Democrats don't want to be associated with him.