Well-known liberal and conservative political donors left the sidelines and injected tens of millions of dollars into the presidential race over the past six months. And once again, it was a tiny group of individuals and businesses who gave a great deal of the money now being deployed in the presidential nomination fights.

Reports filed with the Federal Election Commission on Sunday — just hours before Iowa voters were to bring the frenzy of campaign activity in their state to a temporary halt as they caucused for their preferred candidates — showed some campaigns and super PACs falling far behind in the money race as others capitalized on good debate performances and the public’s discontent with Washington.

Data collected from the filings of 21 different super PACs supporting the top 13 major party candidates (not including former Sen. Rick Santorum or former Virginia Gov. Jim Gilmore) show 29 individuals or organizations who gave $1 million or more, and even that slice of the overall $99.4 million raised by those groups is concentrated at the top.

With a $6 million contribution to a super PAC backing Democratic former Secretary of State Hillary Clinton, Priorities USA Action, liberal billionaire George Soros took the prize for biggest individual contribution. He’s still $4 million behind the largest single contribution, a $10 million drop from Hank Greenberg through his insurance conglomerate C.V. Starr & Co. to the super PAC supporting former Florida Gov. Jeb Bush, Right to Rise USA.

That $99 million will remain out of the candidates’ reach, legally speaking. The money given to the super PACs backing them isn’t theirs to spend, and the last six months saw several candidates — former Texas Gov. Rick Perry and Wisconsin Gov. Scott Walker, most notably — drop out of the race despite millions of dollars at the disposal of super PACs supporting their candidacies.

Much of that money was simply refunded to the mega-donors who gave it. Candidates doing well on the campaign trail, though, generally had little trouble raising “hard money” for their campaign committee’s expenses.

All told, the 21 major single-candidate super PACs and 13 campaign committees we counted raised $260 million in the last six months of 2015.

Donors step off the sidelines

Greenberg is best known as the former CEO of

Singer

Bush, like his super PAC, struggled. He took in just $7.1 million, almost all of it from individuals giving more than $200. And he spent $9.8 million – about $2.7 million more than he received in the last quarter of the year. He still had close to $7.6 million in the bank at the end of December due to contributions he’d received early in the race.

New Jersey Gov.Chris Christie, Bush’s opponent in the GOP “establishment lane,” or the real estate on the political spectrum also sought by Rubio and Ohio Gov. John Kasich, didn’t fare much better.  Much of the wind, such as it was, went out of Christie’s campaign in the last part of the year: He raised just $2.9 million and spent $3.2; in the previous quarter he had managed to bring in $4.2 million. His stockpile of cash was down to $1.1 million.

Meanwhile, the Republican front-runner, billionaire real estate titan Donald Trump, pulled in about $2.1 million from small donors – about four times as much as he got from large contributors.

But the bulk of his funding came from loans to himself: He finally put a serious sum of his own money, $10.8 million, into his campaign, as he’d promised to do. Trump spent close to $6.9 million, and had almost exactly that same amount left in the bank at year’s end.

But Trump can no longer brag that he’s doing it all himself with no outside group gathering big bucks to support him. In January, TrumPAC was launched by by William Doddridge, CEO of the Jewelry Exchange, and Amy Kremer, former chair of the Tea Party Express. It’s first fundraising report has yet to be filed.

Researcher Alex Baumgart and reporting intern Alex Glorioso contributed to this story.