Fredreka Schouten and Christopher Schnaars

USA TODAY

WASHINGTON — Many of the wealthy Republican contributors who raced to write seven-figure checks to influence the nomination battle have shut their wallets on GOP nominee Donald Trump, directing their money instead to downballot contests or opting to sit out the campaign, a USA TODAY analysis of new campaign filings shows.

Some of the nation’s richest Democrats, meanwhile, have escalated their giving to boost Hillary Clinton’s presidential hopes and to seize on the prospect of a Democratic takeover in the Senate, according to the review of contributions by the election’s most generous donors.

Wealthy Democrats and liberal organizations have plowed $134 million into super PACs since early April as Clinton pulled away from rival Bernie Sanders and Trump won a string of primaries on his way to effectively clinching the GOP nomination in early May. By comparison, the Republican Party’s biggest donors contributed $51 million to super PACs during the same period.

The three largest beneficiaries of the Democratic money surge: a pro-Clinton super PAC, a group funded and run by California environmentalist Tom Steyer and a Senate-focused group that just posted its best fundraising haul of the election.

The USA TODAY analysis identified the 156 individuals, corporations and organizations that have donated at least $1 million to super PACs since Jan. 1, 2015, and reviewed their month-by-month giving.

Those donors, some of the richest people in the country, account for nearly 60% of the record $969.2 million that has flowed to super PACs through the end of July. Super PACs can accept unlimited amounts of money but are not allowed to coordinate their advertising with candidates for federal office.

Five people, all of whom made their fortunes running hedge funds, have contributed $15 million or more each to super PACs. Only one, Renaissance Technologies co-founder Robert Mercer, is backing Trump.

Some of the Republican Party’s biggest contributors who still remain active in super PAC giving are directing money to groups intent on preserving the party’s majority in the Senate and the House.

Early in the 2016 campaign, California investor William Oberndorf contributed more than $1.5 million to a super PAC supporting Republican Jeb Bush’s presidential bid. The hedge-fund manager refuses to back Trump’s campaign and donated $500,000 in late June to the Congressional Leadership Fund, a super PAC closely aligned with House Speaker Paul Ryan, R-Wis., that has seen its fundraising climb this year. He’s also contributed $25,000 to a super PAC aiding Ohio Sen. Rob Portman’s battle against former governor Ted Strickland, a Democrat.

“I decided some time ago I could not support Donald Trump because he did not have the temperament to be our next president,” Oberndorf said in an email to USA TODAY. “Since that time, his inconsistency on issues and the offensive remarks he continues to make about virtually anyone who disagrees with him have not given me cause to change this view.”

He said the nation’s debt is a top issue in the election. "The only person on the political scene in a leadership position who is focusing on this crucial issue is Paul Ryan, which is why I am supporting him and his efforts to keep Republican control of the House,” Oberndorf said. “I am also helping those Republican senators who are in tough races with the hope most of them will be able to hold on to their seats as well.”

The stakes in November couldn't be higher. Republicans are defending 24 Senate seats in November to the Democrats' 10. Compounding Republican troubles: Seven of the party's Senate incumbents are up for re-election in states won by President Obama in 2008 and 2012.

Democrats, seizing on Trump's difficulties in the presidential race, also have begun to target more GOP incumbents in the House in the hopes of cutting into the Republicans' 59-seat advantage in that chamber. Democrats need a net gain of 30 seats to take the majority.

In response, the Ryan-affiliated Congressional Leadership Fund announced plans this month to direct $10 million to a dozen competitive House contests. Its fundraising jumped from $1.4 million to $4.6 million between the first and second quarters of this year.

The group does not have to disclose its third-quarter totals until later this year, but giving has “exponentially increased,” driven by donor concerns about the races at the top of the ticket, along with contributor support for Ryan and his policies, said Mike Shields, the group’s president.

“They are worried they could be facing a President Hillary Clinton and an uncertain Senate election,” Shields said of donors. “They want to make sure the House is protected because they see the House as a fire-line to stop some really bad policies.”

Elections 2016 | USA TODAY Network

Is it Trump or Clinton?

It’s impossible to track the sources of all the money flooding the 2016 election because so much of it is landing in the bank accounts of nonprofit groups that don’t have to disclose their donors’ identities. Nonprofits already account for nearly half of all TV ads by groups active in Senate races, according to a recent analysis by the Wesleyan Media Project.

But the new filings offer a snapshot of the role the super wealthy play in the election. Just three dozen people, corporations and unions account for more than one-third of giving to super PACs, the analysis found.

Steyer, a retired hedge-fund manager and a Democrat, sits atop the mega-donor list, contributing more than $38 million, most of which went to his own super PAC, NextGen Climate Action. The group plans an aggressive effort to turn out young voters and union members to vote for Democrats in several key battlegrounds.

Steyer said he doesn’t have a specific budget in mind for his 2016 spending. On Tuesday, he announced a $2 million campaign with the Service Employees International Union and Planned Parenthood Votes to reach some 200,000 voters in New Hampshire, a presidential battleground and the site of the hotly contested Senate race between first-term Republican Sen. Kelly Ayotte and the state’s Democratic Gov. Maggie Hassan.

“We are committed to doing everything in our power to deliver (Trump) a resounding defeat on Nov. 8,” Steyer said of his joint efforts with the union and Planned Parenthood.

Mercer, a reclusive New Yorker, is the second-largest super PAC donor of the election. He has contributed more than $20 million to super PACs, more than half of which went to support Texas Sen. Ted Cruz’s failed bid for the nomination.

He’s now backing Trump and donated $2 million last month to a super PAC that once supported Cruz but has been re-named Make America Number 1 as a vehicle to help Trump. In addition, veteran pollster Kellyanne Conway, who ran Mercer's pro-Cruz super PAC, now manages Trump’s campaign.

Another pro-Trump super PAC, Rebuilding America Now, appears to be better funded, having spent more than $13 million on advertising in recent weeks, but it does not have the file disclosure reports on its donors until October.

Trump camp endorses a super PAC

Officials with the super PAC won’t discuss how much they’ve raised since the end of June. Spokeswoman Melissa Stone said Rebuilding America Now “has connected with many donors excited to expose Hillary Clinton’s record of corruption." But she said what "we have received still pales in comparison to the Clinton money machine."

Bush's early fundraising success helped drive the big giving by Republicans at the start of the election. A pro-Bush super PAC, Right to Rise, collected a record $118 million, but the former Florida governor never gained traction and dropped out of the race following his fourth-place finish in the South Carolina primary.

The super PAC's organizers recently refunded $13.9 million to donors.