Outside spending nears $2 billion – and the biggest groups pull further ahead

Outside groups have poured nearly $2 billion into this election cycle with weeks of spending still to come, and a small cluster of groups is responsible for a growing share of that money.

The top six outside groups – the Senate Leadership Fund, Texas PAC, No Going Back PAC, WinSenate PAC, the Congressional Leadership Fund and Americans for Prosperity Action – spent more than $60 million apiece as of Oct. 5, according to federal disclosure reports analyzed by OpenSecrets.

Together, they accounted for more than $678 million – or more than a third of the outside spending by 794 groups tracked by OpenSecrets, and a sum nearly equal to the combined spending of the next 34 groups. Just 16 organizations account for more than half of all outside spending during the current cycle.

Each of those groups serves a distinct purpose. For example, the Senate ...