These spending data indicate that liberal and conservative outside groups along with the national parties were all pouring money into the same relatively small set of races that were considered competitive, and there was almost perfect agreement about which races those were. Moreover, even though they are not legally allowed to “coordinate” with each other, the outside groups and parties track each other’s spending closely: If they see other groups or parties spending money on a race, they spend money; if they don’t, they don’t. This can be seen from the fact that neither outside groups nor the parties spent a significant amount of money on the Virginia Senate race — a race that shocked everyone by turning out to be extremely close.
The fact that vast sums of money were being spent by liberal and conservative groups along with the national parties on the same small set of Senate races probably limited the impact of such spending. Not only was one side’s spending generally matched by the other side’s spending, but the sheer volume of spending probably exceeded the point of diminishing returns in many of these states. For example, after each side had spent $30 million on attack ads in a small state like Iowa, it’s hard to believe that an additional $1 million in spending on attack ads by either side was going to have much impact on the Hawkeye State electorate — except perhaps causing more Iowans to turn off their televisions.
Republicans made major gains in the 2014 Senate elections but the findings reported here indicate that outside spending by conservative groups had little or nothing to do with those gains. The main reason why Republicans did very well in 2014 was that Democrats were defending far more seats than Republicans and many of those seats were in states that normally favor Republicans based on recent presidential voting patterns. Democrats lost all seven of their seats in states carried by Mitt Romney in 2012 even though Democratic candidates enjoyed an advantage in outside spending in several of those races.
The factors that limited the impact of outside spending in 2014 are very likely to be present in the 2016 elections as well. In the large majority of states, the winners of the presidential and Senate elections will be determined by the relative strength of the parties in the state. In the last four presidential elections, 40 of the 50 states have supported the same party in each contest, and there is little reason to expect anything different in 2016. In the 2016 Senate elections, Democrats are likely to gain at least a few seats simply because Republicans will be defending a large number of seats in blue states that they picked up in the 2010 midterm election. Notwithstanding the plans of the Koch network to spend almost $900 million on the 2016 elections, neither party is likely to enjoy a substantial advantage in spending in the relatively small number of competitive states that will decide the presidential election or control of the Senate.