In 2008, Sen. John McCain returned $50,000 when questions arose about how its donor had scored a defense contract. In February, President Obama returned more than $200,000 donated by several men linked to drug and assassination allegations in Mexico. These decisions reflected the basic calculation that it is worth more, politically, not to be tainted by questionable funds than to have the money to spend. Given the comparatively paltry sums, they were no-brainers.

But what about when many, many millions of dollars are at stake? What about when the donor is Sheldon Adelson, and he has given or pledged to give more than $70 million (!) to Republican groups this cycle? When he was put front-and-center at Mitt Romney’s speech in Jerusalem, and when Rep. Paul Ryan is headed to a fundraiser at the Adelson-owned Venetian three days after being announced as the vice-presidential nominee? What happens when a donor is, in effect, too big to fail? (Disclosure: I totally lost some money at the Venetian’s blackjack tables three years ago. It’s not the source of my agitation.)

The Las Vegas-based multibillionaire casino magnate has exploited the breakdowns in campaign-finance law following the Citizens United decision to become the most influential political donor in the United States—he basically single-handedly kept Newt Gingrich’s primary candidacy afloat through January by giving a supportive SuperPAC more than $15 million—even as more revelations about the questionable ways in which he amassed his fortune have trickled out.

The classic of the genre was Connie Bruck’s 2008 New Yorker profile, which rehashed Adelson’s run-ins with the Culinary Union in Nevada and businessmen in Macao, the Chinese island-territory where Adelson has made the vast majority of his riches over the past decade. Bruck reported that Adelson had used political connections (to then-House Majority Whip Tom DeLay) to quash a resolution condemning Chinese human rights abuses at the same time that he was hoping for favorable treatment when China lifted a monopoly on gambling in Macao. In 2010, a former employee's lawsuit alleged that Adelson at the least passively accepted the involvement of organized crime in his casinos and effectively hired a Macau legislator. A new New York Times story refers to a Chinese businessman’s allegation that Adelson’s Sands company used him as a front to purchase real estate in Beijing and engaged in “blackmail and bribery” to buy a Chinese basketball team in a similar fashion. Reportedly, both Chinese and U.S. authorities are investigating.

I do not know whether any of these allegations are true, and I’m not going to say they are: partly because I really don’t know, partly because I don’t want Adelson to sue me, as he has the National Jewish Democratic Council, which cited a report that he had “personally approved” of prostitution at his Macau properties. Adelson’s company denies all of these charges.