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WASHINGTON (AP) - Corporations and labor unions have been emboldened this election season to spend unlimited sums of cash.

The Supreme Court is telling them to go full speed ahead.

The high court on Monday reaffirmed its controversial Citizens United decision from 2010, following a challenge to a Montana law that prohibited corporate spending in elections. But the court's decision in the Montana case probably will mean a push for more campaign-finance deregulation.

In the middle of a presidential race already brimming with cash from "super" political committees, the decision leaves no ambiguity that the practice can continue. That benefits the campaigns of President Barack Obama and Republican Mitt Romney the most.

Super PACs so far have spent tens of millions of dollars on the presidential election.