The National Republican Congressional Committee reported spending more than $800,000 on one day, Friday Oct. 1, in opposition to 30 Democrats. The NRCC has spent almost $13.7 million in independent expenditures to oppose Democrats so far this election cycle, tops among all groups as of this writing.
Though Super PACs or independent expenditure-only committees–groups set up to take unlimited funds from any source in order to influence elections–have garnered a great deal of media attention of late, it's worth noting that the traditional players like the NRCC are still very powerful when it comes to influencing elections.
The money was largely spent on media buys, which translates to tv, radio or newspaper ads. The top donors to the NRCC are campaign committees of Republican House leaders.