- Katy Bachman, Mediaweek

The U.S. Supreme Court today in a 5-4 decision struck down part of the McCain-Feingold campaign finance bill that limited how much money corporations, unions and other organizations could spend on political advertising. As part of the ruling, the Supreme Court also lifted a rule that barred unions and corporations from spending close to Election Day.

The decision opens the door to more groups that wish to influence the masses via advertising dollars. Just how much more money will be spent in measured media during this year's midterm congressional election is hard to gauge.

Even before today's landmark decision, forecasters had predicted a record year of political spending to exceed $2.6 billion, and possibly topping $3 billion. Broadcast TV, which gets about 67 percent of the total ad spend, has the most to gain.

Evan Tracey, president of TNS Media Intelligence's campaign media analysis group, said most forecasts had taken into account a likely change in the campaign finance rules.

"It will add more at the margins by expanding races that will see this spending as we get closer to Election Day," said Tracey.