This election cycle is flush with outside spending. As of today, super PACs, social welfare 501(c)(4) groups, trade associations, unions, parties and others (corporations, individuals etc) have spent 
Outside spending for and against Hillary Clinton by single-candidate super PACs dominates the 2016 Democratic presidential primary.
Outside spending for former Florida Gov. Jeb Bush still dominates on the GOP side, even after his super PAC fundraising recently fell off a cliff.
Super PACs, which can take unlimited amounts from virtually any source but must disclose their donors, have gotten an early start this cycle. On this date in 2012 and 2014, there were only 43 and 58 of them, respectively. Today, there are 2,206 super PACs, though only 84 of them are spending money. So far, they’ve laid out $189.1 million, more than 300 percent more than they’d spent by this time in the last presidential election.
Among 501(c)(4) dark money groups – so-called because they aren’t required to disclose their donors – 21 fewer are active so far this election cycle compared with 2012, a total of 28 groups. Even though there are many fewer groups this cycle, however, they’ve spent almost three times as much: $4.2 million versus $1.4 million. All nondisclosing groups (including (c)(4) organizations) have spent$8.7 million so far, compared with $4.9 million at this point in 2012.
And that’s only going to soar, if the pattern of 2012 repeats itself. By the time that election was over, groups that don’t disclose their donors had spent $308.7 million — 63 times their Feb. 12 number.
There are almost twice as many conservative dark money groups as there are liberal.
These conservative groups are spending almost 10.5 times the amount the liberal groups are. That’s similar to what happened in 2012, but the difference between conservative and liberal spending is more exaggerated.
(Caveat: Outside spending is, by nature, murky. Corporations and unions can support candidates as long as they are not coordinating with the campaigns. This support often takes the form of television advertising — not all of which is reported to the FEC, depending on who’s sponsoring the ads and when they run.)
Presidential candidates aren’t the only ones attracting outside spending this cycle.
Club for Growth, US Chamber of Commerce and Americans for Prosperity (AFP) are among the biggest groups weighing in on House and Senate races this year.Ted Strickland, a Democrat running for an Ohio Senate seat, is prey for both the Chamber of Commerce and AFP, the latter of which is the flagship dark money spending group in the Koch network. The Chamber has spent more than $525,000 and AFP almost $1.6 million attacking him, Center for Responsive Politics data show. While Strickland had a slim lead over the Republican incumbent, Sen. Rob Portman, back in June, if money talks, he’s unlikely to maintain that going forward. Portman’s campaign outraised Strickland’s by $12 million in 2015.
Club for Growth has spent a large chunk – $691,000 – on negative ads against Democratic Wisconsin senatorial candidate Russ Feingold., and another $41,000 supporting his Republican opponent, Sen. Ron Johnson. It has also helped support the GOP candidate for Senate in Florida, Ron DeSantis, and the Republican incumbent in Pennsylvania, Sen. Pat Toomey, to the tune of $18,846 and $12,816, respectively.
The Chamber has also spent $500,000 apiece on Sen. Mark Kirk (R-Ill.) and Toomey; $400,150 on Rep. Joe Heck; and $350,150 each on Sens. Kelly Ayotte(R-N.H.) and John McCain (R-Ariz.).
Some congressional candidates are even benefiting from outside spending groups dedicated to them and them alone: Incumbent Rep. Dan Donovan (R-N.Y.) has received $40,000 worth of support from Unifying America PAC, which is funded entirely by USFluence Group. And Portman has received $14,000 in backing from the super PAC Fighting for Ohio Fund.