The defense of Citizens United rests on two primary claims about the case, one factual and one legal. Its defenders contend, first, that while Citizens United only concerned corporate election spending, the facts show that it is spending by individuals -- not corporations -- that counts this year. Next, they argue that, as a legal matter, individual spenders have been free to make unlimited political donations since long before Citizens United. They're wrong on both counts.

It's true that individuals have donated more than corporations to super PACs, but it's misleading to suggest corporate dollars don't matter. A recent analysis by the Washington Times, for example, showed that "nearly 200 companies gave $8.6 million to super PACs in June" -- the highest total yet this year -- including "many repeat givers who have given a total of $18 million."

And corporate donations to super PACs are just the tip of the iceberg. More corporate money is flowing into non-profit "social welfare" groups and trade associations like the U.S. Chamber of Commerce, which spend millions of dollars on electioneering but don't reveal their donors. Corporate donors afraid of alienating customers prefer these groups because they allow the corporations to remain anonymous -- except when a company like Aetna accidentally reveals that it gave more than $7 million to such groups to influence elections. As the New York Times recently reported, secretive tax-exempt groups outspent super PACs by a 3-to-2 margin in 2010, and "such groups have accounted for two-thirds of the political advertising bought by the biggest outside spenders so far in the 2012 election cycle."

Just as misguided as downplaying corporate election spending this year is suggesting that there's nothing new about the unlimited contributions that individuals are making -- like the up to $100 million that casino magnate Sheldon Adelson has pledged to defeat President Obama. Defenders of Citizens United say individuals like Adelson have had the right to spend unlimited sums since 1976, when the Supreme Court decided the seminal campaign finance case Buckley v. Valeo.

True, Buckley struck down expenditure limits -- but it upheld contribution limits. So, after Buckley, Adelson could have made his own political advertisements and bought the air time to run them. But few chose to do so. Most donors prefer not to get their own hands dirty; they'd rather give to political action committees run by campaign professionals. Before Citizens United, there were strict contribution limits on how much an individual could donate to a PAC.

Some tried to circumvent these limits by giving to so-called 527s -- like the Swift Boat group in 2004 -- but as election law expert Rick Hasen has written, doing so was of dubious legality. The FEC levied fines of several hundred thousand dollars against 527 groups after they got involved in the 2004 election. Hasen explains that if Adelson had donated tens of millions to a 527, "you can bet that there would be a criminal investigation and very serious charges considered."