This year’s media campaigning is on track to be the most expensive midterm election ever. The Center for Responsive Politics (CRP) projects that by the time the polls close on Tuesday, November 4, the candidates and parties alone will have spent $2.7 billion on the congressional and state races. The independent groups are expected to spend nearly $900 million, which is impressive compared to the $1.3 billion they spent in 2012 when there was a hyper-expensive presidential election as well. That all adds up to $3.93 billion—an increase of $333 million from the 2010 midterm election.

CRP projects a slight edge in spending for the Republican side. In all, the GOP, its candidates and conservative-leaning outside groups are projected to spend at least $1.92 billion. Democrats, their party and liberal-leaning outside groups are projected to spend at least $1.76 billion. CRP based its projections on spending totals reported to the Federal Election Commission through June 30 or August 31, depending on which FEC filing schedule each filer used. CRP also notes that there are some “issue ads” that don’t have to be reported to the FEC as election advertising.

With the hotly contested battle for control of the U.S. Senate going down to the wire, CRP calculates that Super PACs and other outside groups are spending $19.4 million per day. So far the liberal groups have spent $308.9 million and the conservative groups $327.1 million. But with heavy spending in the final days of the campaign, CRP is projecting that the liberals will finish slightly ahead in the dollar tally—spending $433 million to the conservatives’ $424 million.