Adelson can afford it. He's the eighth-richest person in America, according to the Forbes list, worth an estimated $21.5 billion.
Every candidate needed at least one megabucks buddy to have a shot at the Republican nomination this year. Wyoming investor Foster Friess, for example, handed Santorum's group more than $2 million.
Romney has the widest circle of wealth. His super PAC reports more than a dozen givers of at least $1 million. Its counterpart on the Obama side lists three: late-night comic Bill Maher, gardening guru Amy P. Goldman and DreamWorks Animation chief Jeffrey Katzenberg, who kicked in $2 million.
Before 2010, individuals could legally spend their own money creating "independent" ads, but without well-organized, candidate-endorsed groups in place to run things, hardly anyone ever did. Those who wanted to put big money behind a candidate sometimes dabbled in gray areas of the law instead.
Billionaire investor George Soros pumped about $1.5 million into the liberal group Moveon.org's campaign to vilify President George W. Bush in 2004. Wealthy conservatives backed the "swift boat" ads attacking Democratic nominee John Kerry. One of them, Texas homebuilder Bob Perry, is now the biggest supporter of the Romney super PAC, giving $4 million.
American elections haven't seen freestyle spending like this since the post-Watergate reforms of the 1970s mandated disclosure of donors and limited contributions.
4. Big business invited in
Companies and unions can play the super PAC game, too. So far businesses and organizations have given just under a fourth of super PAC money, according to the Center for Responsive Politics.
Publicly traded corporations may fear offending stockholders or customers, however. Gay rights activists protested loudly when Target Corp. donated $150,000 to a super PAC supporting a Minnesota gubernatorial candidate who strongly opposed gay marriage. The company apologized.
Corporations may prefer backdoor avenues of giving that also are opening wider to them under the new rules.
"You can imagine the scenario in which a Microsoft or Google or Facebook decides, 'This election really matters. What's another $20 million?'" said Brigham Young University professor David Magleby, who studies campaign finance.
And they could be pressured to give.
Michael J. Malbin, executive director of the nonpartisan Campaign Finance Institute, worries about a return to the days of President Richard Nixon's campaign shaking down corporations. "Unlimited contributions became temptations for officeholders to twist the arms of potential donors and come just one step short of criminal extortion," he said.
5. Donors hiding in the shadows
Super PACs are required to list their contributors, but some big givers stay secret by going through other channels.
Publicity-shy people and companies can give to advocacy groups that don't have to disclose their donors, because ostensibly they are focused on issues or the good of society, not candidates. These tax-exempt groups for years have spent millions on things like prodding people to the polls, voter registration, and "issue ads" that sometimes look more like attack ads.
Now they can act in the open — spending much of their money on ads to directly support or, more often, oppose candidates. The state of the law is fuzzy, but it appears court rulings have cleared issue groups to spend almost half their budgets this way.
They include old standard-bearers like the U.S. Chamber of Commerce, plus newbies such as Crossroads GPS, created by Republican Karl Rove, and a pro-Obama group, Priorities USA. Those two are sister organizations to super PACs with similar names, and could become a path for unnamed donors into those committees.
Crossroads GPS told the IRS it raised more than $77 million through December. Donors could include individuals, businesses or trade groups. Without naming names, Crossroads reported two gifts of $10 million each and four of more than $4 million.
6. Outside money swamping congressional campaigns