WASHINGTON (AP) — Look no further than Iowa to understand the impact of a Supreme Court ruling that opened the floodgates to outside money in American politics — and to get a glimpse of what's in store for the race between President Barack Obama and the eventual Republican nominee.

Independent groups called super political action committees have spent millions on television ads and mailings to boost their favored candidates in Iowa and maim those candidates' rivals, dramatically influencing what's been a remarkably fluid race for the GOP presidential nomination.

The groups have ramped up spending just as the primary season is hitting full-force. Some have done the campaigns' bidding by running attack ads on rivals. Others have bolstered candidates who had been running on financial fumes.

The trend will hardly be unique to Iowa. Political operatives and campaign-finance watchdogs say the 2012 election — projected to be among the costliest ever — will face an onslaught of ads by powerful interests that will have an extraordinary say in who might next occupy the Oval Office.