Updated

Big outside political groups armed with an unprecedented river of money had appeared poised to be pivotal players in the 2012 elections.

So far, these super PACs are looking less than super.

Freed of any constraints on the size of donations, political action committees have since April poured more than $250 million into the presidential and select congressional races—more than what the two 1996 presidential candidates spent in total on their campaigns, records show.

But signs are few that super PACs have had the major impact that both supporters and critics predicted. 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.

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