1. Farris and Dan Wilks
Farris and Dan Wilks and their spouses donated $15,000,000 to Ted Cruz's super PAC, Keep the Promise. The Texas brothers, along with their spouses, are billionaires and frequent donors to socially-conservative nonprofits. Until now, they've kept out of the spotlight, but due to disclosure requirements for political donations, their names are out there as big political players.
2. Robert Mercer
Robert Mercer is a Wall Street hedge fund manager who started at IBM and made his money using computers to predict the stock market. His misgivings about the IRS and climate change align him closely with Cruz, which is probably why he donated $11,300,000 to Ted Cruz's Keep the Promise PAC. Still, a good investor knows to diversify his portfolio, and Mercer has also donated a little to Bobby Jindal and Carly Fiorina.
3. Toby Neugebauer
Toby Neugebauer is a Texan-turned Puerto Rican who moved to the island seeking tax shelter after making billions with his private equity firm Quantum Energy Partners. His uneasiness over the whole "taxes" thing probably has a lot to do with him throwing $10,000,000 behind the Tea Party-leaning Cruz. Neugebauer, along with Mercer and the Wilks brothers, were just about the entirety of Cruz's record-breaking $36M fundraising right out of the gate.
4. Kelcy Warren
Dallas Billionaire Kelcy Warren is chief executive of Energy Transfer Partners. His $6,000,000 donation to Rick Perry's PAC, the Opportunity and Freedom PAC, raised some eyebrows as Warren was serving as Perry's campaign finance advisor at the time and laws strictly regulate the interaction that campaigns and PACs have. In the end, it didn't matter, anyway. Perry withdrew from the running in September.
5. Joe and Marlene Ricketts
Joe Ricketts, founder of TD Ameritrade, and his wife Marlene donated $5,000,000 to Walker's super PAC, Unintimidated. The two bonded over their Midwestern backgrounds and views on spending. Walker, of course, ended his campaign in September 2015, and is currently soliciting donations to pay off the $1,000,000 or so in debt that his campaign currently owes.
6. Darwin Deason and Family
Darwin Deason is the billionaire founder of Affiliated Computer Services. He threw $5,000,000 of support into Rick Perry's presidential campaign but actually launched a bid to get his money back since Perry dropped out of the race.
7. Diane Hendricks
Wisconsin billionaire Diane Hendricks donated $5,000,000 to Scott Walker's campaign. Hendricks and Walker bonded over a shared anti-union stance among other things. Hendricks has long supported Walker financially, including his fight to stave off a recall in 2012. There's no word as of yet on whether she'll help him settle his accounts with the now-defunct PAC's debts.
8. Miguel "Mike" Fernandez
Jeb Bush's fundraising hasn't been nearly as dramatic as Ted Cruz's, but his political position is still strong (most of it coming from the Republican establishment as opposed to Tea Party elements). Bush outraised all of his rivals, both Republican and Democrat, in the first half of 2015, and yet Mike Fernandez's $3,200,000 donation is the only Bush donation on this top 10 list. Fernandez describes himself as a "compassionate conservative," and cites Bush's substance and executive experience.
9. Honorable Mention: George Soros
Soros has thus far only donated $1,000,000, to Hillary Clinton. However, he's thrown $5,000,000 into the fight against voter restrictions, siding with the Democrats on an issue that's very heavily tied to the outcome of the election. His contributions to an actual campaign aren't much so far, but his political spending would easily put him in the top half of the list as it stands today.
10. Honorable Mention: The Koch Brothers
While the Kochs haven't yet thrown their support behind a candidate, they're clearly setting themselves up to be conservative kingmakers. The pair famously budgeted some $889,000,000 in political spending, and while not all of that is for the election, their presence will be felt when they do decide to step in the ring. The brothers made headlines in July 2015 when they held a bizarre Southern California confab with four of the GOP frontrunners, and they're clearly weighing their options.