In a campaign characterized by big donors, casino mogul Sheldon Adelson and his wife, Miriam, stand out. The couple's latest blizzard of political check writing — which produced more than $15 million of donations to Republican candidates and causes in a one week period this month — brought their total political contributions for the 2012 cycle to a whopping $52 million.

The next closest big campaign donor, billionaire nuclear waste entrepreneur Harold Simmons, has given $23 million.

The Adelsons lead a roster of 134 individuals or organizations giving $1 million or more to campaigns in this, the first presidential campaign to take place after Citizens United, the 2010 Supreme Court decision that opened the door for unlimited campaign donations. The $375 million that they have donated represents more than half of the money collected by super PACs in the 2012 election cycle. 

What the impact is of such outside influence remains to be seen. But some of the items on the Adelson's agenda already are clear: Sheldon Adelson's casino empire, which stretches from Bethlehem, Pa., to Macau, China, is in the midst of a multi-year battle with the IRS over taxes. Moreover, he and his wife — who began her medical career in Israel — are backers of an aggressive foreign policy on behalf of the Jewish state.

The Adelsons, who initially favored former House Speaker Newt Gingrich's presidential campaign, contributing $15 million to Winning our Future, the super PAC supporting him (on top of having contributed about $7 million to another outside group that supported him in earlier elections). But after Mitt Romney bested his rivals for the GOP presidential nomination, the Adelson turned their largesse in his direction. This month, they gave another $10 million to Restore out Future, the super PAC supporting Romney.

Adelson was invited to be part of Romney's entourage when he visited Israel earleir this year. Adelson has said that he planned to spend up to $100 million or "whatever it takes" to defeat Obama.

Some other outside groups that have benefitted from the money from the power couple including $5 million to the Congressional Leadership Fund–the group that spending on electioneering opposing Democrats and the YG Action Fund–the super PAC backed by House Majority Leader Eric Cantor, R-Va. The Adelsons have also spread some of their wealth to smaller outside groups supporting GOP House and Senate candidates such as Freedom PAC and Independence Virginia PAC.

Here is a tally of some of the top donors to super PACs which includes individuals, labor groups and corporations, based on a quick analysis of the latest FEC filings by Sunlight.

For a downloadable file of totals for all donors click here. Please note that this spreadsheet is a work in progress and we continue to refine the numbers.