Read MoreWall Street gears up for 2014 elections
Libertarian-leaning Singer is Exhibit A. He is deeply distrustful of Democratic leadership and policies like monetary stimulus and the Affordable Care Act. Washington's poor leadership, Singer has said, could cause economic disaster when combined with similarly poor fiscal stewardship around the world.
"Nobody can predict when things will unravel, how the unraveling will take place, or what the world will look like after the next crisis," Singer wrote in a July letter to investors. "But the numbers (debt, derivatives, and promises) are extraordinarily large, the dysfunction very powerful, and the leadership throughout the developed world very weak."
A major private equity donor is John Childs, founder of J.W. Childs. He's given $460,050 to political causes in 2013 and 2014, according to public filings. The most, $300,000, went to American Crossroads, the conservative PAC co-founded by Karl Rove. The group is a major force in the midterms, running television advertisements helpful to Republican Senate hopefuls Thom Tillis in North Carolina, Scott Brown in New Hampshire, and Joni Ernst in Iowa.
Spokesmen for Singer and Childs did not respond to requests for comment.
Mercer avoids public comment but speaks with his checkboook. Recent donations include $500,000 to Women Speak Out, an anti-abortion PAC. Another $1 million this year has gone to a group supporting John Bolton, a potential Republican presidential candidate and backer of other politicians who are seen as strong on defense. Another $900,000 has gone to Club for Growth Action, which works to limit the size of government by backing conservative candidates like Arkansas Senate hopeful Tom Cotton. A spokesman for Mercer declined to comment.
The largest liberal-leaning donor is Tom Steyer, the retired founder of hedge fund firm Farallon Capital Management. Steyer, now a full-time environmentalist, is using his NextGen Climate Action group to attack candidates for their lack of concern on climate change. He has given $37.7 million to NextGen and a related group, CE Action Committee this year and last.
"The debate on climate change is settled: It is here, it is human-caused, and it is already having a devastating impact on our communities, but we need to accelerate the level of political support to address this critical issue before it's too late," Steyer told CNBC.com in May. "This means making politicians feel the heat—in their campaign coffers and at the polls."
Read MorePoliticians fight back as hedge funders ramp up election spending