Las Vegas Sands
When you combine the money contributed by Sheldon Adelson's Las Vegas Sands casino (almost $28 million) and the nonprofit Adelson Clinic for Drug Abuse Treatment and Research ($27 million) run by his wife, Dr. Miriam Adelson, their $55.7 million in campaign contributions for the 2018 cycle alone makes the Adelson family one of the biggest political donors.
According to Bloomberg, Sheldon Adelson has contributed over $200 million to conservative candidates and causes in recent years.
Uline Corporation
The Uline Corporation, run by Richard and Elizabeth Uihlein, sells office supplies through a thick catalog, the print version of which includes conservative political commentary from Elizabeth Uihlein, according to Politico.
Uline has donated $31.7 million so far in 2018, more than it spent for the 2016 cycle, according to Open Secrets. The vast majority of that money went to Republicans. Their soft money donations have soared since the Citizens United decision in 2010.
Fahr LLC
Fahr LLC is a privately owned company that manages the wealth of Tom Steyer, former hedge fund manager and current political activist. According to Open Secrets, Fahr LLC has donated $29.4 million to the current election cycle so far, and that may be just the beginning, since the corporation's 2016 contributions topped $90 million.
Steyer is the driving force behind Need to Impeach, an organization and super PAC trying to get Trump out of office. CNN reported that he has pledged to spend at least $30 million on Democratic candidates for the House of Representatives in 2018, as well as $40 million toward impeachment.
Paloma Partners
Paloma Partners is an investment company founded by S. Donald Sussman, who has quietly contributed millions to Democrats and the PACs that support them. Open Secrets reports that Paloma Partners has donated more than $23 million so far in 2018. In 2016, the contribution was close to $42 million.
Soros Fund Management
With $14 million in political donations so far in 2018 and $28.7 million in the 2016 election year, private hedge fund Soros Fund Management isn't the biggest political donor on the left, but you could be forgiven for thinking it was.
Outspoken George Soros has become a boogeyman to many on the right — he is the target of several conspiracy theories. For example, despite persistent rumors, Snopes confirms that Soros did not pay people to attend the 2018 March for Our Lives.
Euclidean Capital
James Simons, whom Forbes listed as the second highest-earning hedge fund manager in 2018, is president of the private hedge fund company Euclidean Capital. Euclidean Capital has given $9.5 million in campaign contributions to Democratic causes so far in 2018.
Renaissance Technologies
Renaissance Technologies, also founded by James Simons (he is still involved with the company, though he has retired), contributed $9.5 million in 2018, split between both political parties. In 2016, the hedge fund donated $59 million, giving slightly more to Democrats than Republicans.
Citadel LLC
Citadel, an investment firm, gave most of their $8.4 million in 2018 contributions to the GOP. They donated almost $14 million in 2016, with the vast majority of that money going to Republicans.
Koch Industries
The $7.5 million in 2018 contributions from Koch Industries may understate the influence of Charles and David Koch on American politics.
They have also contributed to the American Legislative Exchange Council (ALEC), which promoted laws limiting lawsuits from people with terminal illness as a result of asbestos. Koch Industries own Georgia Pacific, which has been subject to these lawsuits.
Through nonprofit Americans for Prosperity (which also donates millions to further Republican causes), the Koch brothers have organized to defeat transit projects in several cities, according to the New York Times. (Government-funded transit contradicts the brothers' free-market, small-government views, and they also profit from people using cars.)
Blackstone Group
Investment company Blackstone Group has contributed almost $7.4 million in the 2018 election cycle and gave almost $9.5 million in 2016. The company's donors gave more to Democrats in 2016, but favor Republicans so far this year.