Updated

Millions of dollars in television advertisements are blanketing Iowa and reshaping the Republican presidential contest just before the first votes are cast. But unlike in other primary elections, a majority of advertisements are not coming from the candidates themselves, according to media buyers.

Instead, most of the on-air politicking is funded by a new breed of political action committee backing individual candidates -- dubbed the Super PAC -- which has sprung to life this year because of changes in the law.

In fact, Iowa is turning into the coming-out party for this new kind of heavy campaign artillery. Super PACs by law cannot coordinate with campaigns and are free to take donations of any size, whereas donors can give only $2,500 to a candidate during a primary-election season.

Super PACs are helping to produce a bifurcated campaign in which candidate generally offer positive messages under their own name while outside groups supporting them attack opponents. The trend is splitting the field between candidates who have a well-financed Super PAC at their back and the poorer candidates who don't.

"This election is a brave new world," said Jan Baran, a longtime Washington campaign-finance attorney with Wiley Rein. For the first time, this campaign involves "new, unlimited money to support specific candidates outside of the control of the candidates and the political parties."

Outside campaign groups have sought to influence presidential campaigns since at least 2004. But a string of court decisions struck down many restrictions that once limited their ability to spend money on elections. By law, these new groups are legally separate from the campaigns and can't coordinate their activities with the candidates they support.

The new landscape appears to be most helpful to Mitt Romney. While the former Massachusetts governor has raised the most money for his campaign, a Super PAC supporting him has so far spent more money on advertisements in Iowa than Romney's own campaign committee, according to a Republican media buyer.

The group supporting Romney, called Restore Our Future, has led the charge criticizing his opponents, allowing Romney's campaign to focus primarily on positive messages.

"The campaigns can say, 'We're not running negative ads,' and 'That's that other bunch,'" said Mark Lundberg, chairman of the GOP in Iowa's Sioux County. "Both sides of the political aisle say they dislike negative advertising, but this is absolute proof that negative advertising works. We're just seeing the beginning."

The new groups are making themselves felt in Iowa. According to data supplied by the Republican media buyer, Romney has paid for $287,000 worth of TV advertising in Iowa during the week that started Monday, just ahead of Iowa's caucuses next week. But $780,000 is being spent in Iowa by the independent group supporting Romney.

Click here to read more on this story from The Wall Street Journal.