From Open Secrets:
The Center for Responsive Politics projects that more than $5.2 billion will be spent this election cycle, making it the most expensive midterm election ever by a wide margin.
With less than two weeks before election day, $4.7 billion has already been spent by candidates, political parties and other groups such as PACs, super PACs and nonprofits. Prior to this election cycle, no midterm election had surpassed more than $4.2 billion in spending when adjusted for inflation.
The overall estimated cost of the 2018 election would represent a 35 percent increase over the 2014 cycle in nominal dollars, the largest increase in at least two decades.
While Republican candidates are raising funds at record levels, the huge uptick in spending is driven primarily by unprecedented Democratic fundraising. Democratic candidates are projected to spend more than $2.5 billion this cycle, while Republicans are expected to spend approximately $2.2 billion.
Democratic House hopefuls have raised more than $951 million, crushing their Republican opponents’ $637 million haul. Things are closer in the Senate — $513 million to $361 million — but Democrats are still ahead.
In every kind of competitive race — even those in red districts — Democrats are either outraising Republicans or keeping pace.