Money has been at the centre of US politics for decades. Candidate Barack Obama raised $750mn to help him get elected as president. That went down as the most expensive federal election in history - but this year it is due to get even more expensive.

"We have a corrupt system where government is responsive to the donors and not to the citizens .... Companies and rich individuals can spend as much as they want to buy the politicians they want to office."

- Daniel Newman, the executive director of MapLight

Millions of dollars are being spent as the race for the US presidency gets underway, and this year corporations and unions are spending record amounts to influence the election.

As a result of a US Supreme Court judgement, known as the "citizens united" ruling, outside groups such as corporations and unions can now raise and spend unlimited money as long as they do not coordinate with the candidate.

The ruling is being challenged in a number of cities. Critics of it say it empowers corporations with their vast treasure chests over individual donors. The Supreme Court says money is a form of free speech, but critics argue that corporations are not people and therefore do not have the same right to free speech.

Another criticism is that candidates are less likely to be held accountable when negative advertisements are funded by outside interest groups on their behalf.

What are the implications of the "citizens united" ruling? And what effect is the increasing amount of money involved having on US politics?

Inside Story: US 2012 discusses with guests: Anne Kornblut, the White House correspondent for the Washington Post; Daniel Newman, the executive director of MapLight, a nonpartisan research organisation that reveals money's influence on politics; and JD Gordon, who has worked on the Herman Cain campaign as the vice-president of communications.

"They [the advertisements] have a bad impact to the extent that they are not truceful on a significant slice of the viewers and that's all it needs to turn the tide against any candidate who is the victim. Most people actually resist negative ads, they'll go with who their preferences are, but all you've got to do is change 10 or 15 per cent and you can destroy somebody's candidacy."

Ralph Nader, a former US presidential candidate

Source: Al Jazeera