WASHINGTON -- A new oligarchic era of American politics came into full view on Friday, as super PACs disclosed fundraising details showing billionaires bankrolling the 2016 presidential race to an unprecedented degree.

The unlimited-money super PACs account for one-third of all federal election funds raised in the first half of 2015 -- up from 4 percent at this time in the last presidential election. Three-quarters of all super PAC money came from more than 500 wealthy donors, corporations and unions in contributions above $100,000. More than half the money in the presidential race so far -- to super PACs and to campaigns -- came from donors who have given at least $100,000.

For the first time in more than a century, the majority of funding for a presidential election is coming in six-figure or larger checks from corporations and the wealthiest Americans. The presidential campaigns, limited to a maximum of $5,400 from a single donor, raised a combined $128 million. Super PACs supporting those candidates pulled in $260 million, with $208 million from those giving $100,000 or more.

“The 2016 presidential candidates and their individual-candidate Super PACs are wiping out the nation’s anti-corruption candidate contribution limits,” Democracy 21 president and longtime campaign finance reform advocate Fred Wertheimer said in a statement. “In doing so, the presidential candidates and the Super PACs supporting them are creating the kind of system that the Supreme Court has described as an inherently corrupt system.”

The dramatic shift to a campaign finance system built upon outsized contributions of the wealthy and their businesses comes five years after the Supreme Court’s 5-4 Citizens United decision opened the door to unlimited electoral spending by corporations, unions and, individuals so long as it remained independent of candidates.

Overall, super PACs raised $314 million through the end of June, compared with $26 million at the same time in 2011. More than 500 donors have given at least $100,000, for a total of $238 million -- 75 percent all super PAC donations.

The super PAC expansion appears likely to take over much of the political fundraising system, especially at the presidential level.

Super PACs Through June 30, 2011 -- A Small Slice Of Fundraising

Super PACs Through June 30, 2015 -- One-Third Of Fundraising

As an oligarchy of campaign contributors has begun to dominate political fundraising, opposition is mounting, with activists calling for campaign finance reform and a rejection of super PAC politics. In Iowa, a coalition of Republicans and Democrats called Iowa Pays the Price are spotlighting the influx of big money into their state to bring attention to the issue. A group called the New Hampshire Rebellion is calling attention to the trend in the nation’s first presidential primary state.

Former President Jimmy Carter this week took note of what was happening to the nation’s politics as candidates race for larger and larger checks from billionaires and millionaires.

"It violates the essence of what made America a great country in its political system," Carter said in a radio interview July 28. "Now it’s just an oligarchy, with unlimited political bribery being the essence of getting the nominations for president or to elect the president."

Numerous candidates have obliterated the requirement that their super PACs operate independently, by directly coordinating with the groups and raising money for them. Republican Jeb Bush personally raised $103 million for his super PAC during a six-month period when he declared that he was not officially running for president.

Bush raised a combined $114 million, including his official campaign and his super PAC. Of that, 63 percent came from donors giving $100,000 or more. Twenty-four of Bush’s super PAC donors gave $1 million or more.

Much of Bush’s money came from a vast pool of large donors. Unlike the rest of the Republican field, Bush’s Right to Rise super PAC collected $100,000-plus donations from about 300 individual donors. His donor list includes more than 1,000 people, corporations or political committees that gave at least $10,000.

Texas Sen. Ted Cruz (R) racked up 71 percent of his super PAC and campaign fundraising from big donors, almost all of it from three million-dollar contributors: $15 million from the fracking Wilks family, $11 million from New York hedge fund executive Robert Mercer, and $10 million from Texas private equity investor Toby Negeubauer.

Florida Sen. Marco Rubio's (R) campaign and super PAC raised 60 percent of their combined total from six-figure donors, most from million-dollar contributors. He raised $5 million from his longtime personal funder, luxury car dealer Norman Braman, $3 million from Oracle CEO Larry Ellison, $2.5 million from a thoroughbred horse stable owned by Benjamin Leon and $2 million from the Israeli-American wife of the Marvel Entertainment CEO, Laura Perlmutter.

Wisconsin Gov. Scott Walker (R) hasn't reported any fundraising for his official campaign. But two unlimited money groups working for him had raised $26 million. Those groups raised 77 percent of their money from donors giving more than six figures. Like other candidates, Walker's groups were predominantly funded by a few million-dollar checks, including $5 million from Wisconsin roofing billionaire Diane Hendricks, $5 million from Chicago Cubs owners Marlene and Joe Ricketts, $2.5 million from Richard and Elizabeth Uihlein, and $1 million from Access Industries, a company run by billionaire Len Blavatnik.

New Day for America, a group that has since converted into a super PAC, supports Ohio Gov. John Kasich (R) and raised more than $11 million, with 86 percent from those giving more than $100,000. Four gave $1 million.

The same can be said for nearly every candidate on down the line: Six-figure donors fueled 85 percent of New Jersey Gov. Chris Christie’s (R) super PAC fundraising; 62 percent for two groups backing Louisiana Gov. Bobby Jindal; 83 percent for former Texas Gov. Rick Perry’s (R) groups; 83 percent for Sen. Lindsey Graham’s (R-S.C.) super PAC; more than 90 percent for three groups supporting Sen. Rand Paul (R-Ky.); and 62 percent for former tech CEO Carly Fiorina’s super PAC.

Some big billionaire names were absent from the list of Republican presidential candidate megadonors, including casino magnate Sheldon Adelson, hedge fund billionaire Paul Singer and the industrialists Charles and David Koch.

While the big-money race on the Republican side of the presidential campaign is most intense, it's not absent from the Democratic Party. Frontrunner Hillary Clinton’s super PAC, Priorities USA Action, a hand-me-down from President Barack Obama, raised $15.6 million, with 99 percent of it coming from $100,000-plus donors. Her group raised nine $1 million checks from George Soros, Haim and Cheryl Saban, Jeffrey Katzenberg, Steven Spielberg, Herbert Sandler, Donald Sussman, a union for plumbers and pipefitters, and a union-backed political group.

Vermont Sen. Bernie Sanders (I) eschews the big-money super PAC race. Former Maryland Gov. Martin O’Malley’s (D) Generation Forward raised $290,000.

Large super PAC fundraising also occurred outside the presidential race.

Billionaire environmentalist Tom Steyer donated $5 million to his personal super PAC, NextGen Climate Action Committee. The United Brotherhood of Carpenters, the AFL-CIO and United Steelworkers each gave more than $1 million to their own super PACs. Singer, who so far has not put his chips down in the presidential race, gave more than $1 million to his super PAC in support of Republicans who favor gay marriage (of which there are very few). And then there’s Cruz’s benefactor, Mercer, who gave $1 million to a super PAC controlled by the neoconservative former United Nations Ambassador John Bolton.

A new super PAC launched by Senate Majority Leader Mitch McConnell (R-Ky.) to support his Republican majority pulled in three $1 million donations, from Houston Texans owner Robert McNair, Home Depot co-founder Bernard Marcus and Singer.