In politics, this is the year of big money. It's the first presidential race since two court decisions in 2010 changed the rules.

Now political groups that operate "independently" of the candidates can spend millions running TV ads on their behalf and attract billionaire donors to pay for it.

They're called "super political action committees." Mitt Romney and Barack Obama each have a group like this, endorsed by the candidates themselves and set up by their former aides.

Wealthy donors also are pumping millions of dollars into political ads without divulging their names, by supporting groups such as the Republican-backing Crossroads GPS.

These tax-exempt groups can now promote or oppose candidates, so long as that's not their primary purpose.

They're spending big on ads in congressional races, too.