The flood of spending doesn’t appear to have significantly influenced voter opinion in key states in the presidential contest or in top congressional races.

On the presidential front, conservative outside groups backing Republican candidates say they already have played their most significant role, and that their influence will fade as the candidates themselves present their closing arguments to voters.

“We believe we have kept a number of races competitive and put important issues on the table. But at this stage of the game, we are no longer the market leader,” said Steven Law, who directs two of the biggest right-leaning outside groups, American Crossroads and Crossroads GPS.