Some longtime Democratic donors have been quiet so far, including trial lawyer and Baltimore Orioles owner Peter Angelos, Sun Microsystems co-founder Vinod Khosla, and former New York Giants owner Bill Neukom. And the Clinton and Sanders campaigns are neck-and-neck in terms of fundraising: as of March, Clinton has raised $189 million while Sanders has brought in $184 million.
Meanwhile, Clinton has already spent more than $129 million on the primary and may be looking to deep-pocketed donors like these to step up for a general election run. Her campaign said it had $29 million in the bank as of April 1.
Pro-Clinton outside groups, including super-PACs Priorities USA, American Bridge 21st Century, Correct the Record and Ready PAC, have spent little on the primary and have about $44 million on hand, FEC records show.
"We set ambitious goals to ensure we'd have the resources we need to win a competitive primary and we've blown past every goal," said Josh Schwerin, a spokesman for the campaign, who noted that half of its support had come through small, online donations. "We've out-raised every opponent." he added, "and are even ahead of President Obama's 2012 pace for primary fundraising."
Through the end of February, Clinton's campaign had raised about $18 million more than Obama had by the same point in 2012. However, Obama didn't face a primary challenger, so he had $104 million on hand in April 2012, more than triple what Clinton now has in the bank.
Vin Ryan isn't the only past Priorities USA donor to support Sanders. Investor Henry Jarecki and video-game designer Alex Rigopulos, who each gave about $100,000 to Priorities USA in 2012, haven't contributed to the super-PAC this cycle but gave the maximum $2,700 to Sanders' campaign. Dick Harpootlian, a former chairman of the Democratic National Committee who gave $25,000 to Obama's re-election, has endorsed the Vermont senator.
"The mood of the country and the mood of the party have changed," Harpootlian said. "And she hasn't changed."
Sandor Straus, a former partner at hedge fund Renaissance Technologies, has given to both Democratic candidates. In February 2015, Straus contributed $100,000 to American Bridge, the opposition research super-PAC founded by Clinton supporter David Brock, and in July of that year sent $500 to Sanders.
Phone calls seeking comment from Angelos, Jarecki, and Rigopulos weren't returned. Khosla, Neukom and Straus declined to comment.
Angelos, who supported Clinton when she was in the Senate through her leadership PAC and re-election campaign, hasn't contributed to her presidential run. Angelos gave $272,000 last year to a group trying to persuade Vice President Joe Biden to enter the 2016 race. In 2012, Angelos gave $500,000 to Priorities USA and the maximum $2,500 to Obama for the primary and general election. He also supported Bill Clinton's presidential re-election effort in 1996, giving $2,000 to the campaign and another $100,000 to the DNC.
There are signs that some money could start to flow should Clinton win the primary. Ken Levine, president and chief executive officer of data security firm Digital Guardian, said he made a contribution to Clinton's campaign at the end of March, but isn't sure whether he'll support any of her super-PACs.
Levine, who gave $50,000 to Priorities USA and $61,600 to the DNC in the 2012 election cycle, said that he thinks Clinton is well-qualified to be president, but is concerned that she won't inspire the kind of turnout needed to win a general election.
"There's definitely a palpable excitement gap," Levine said, adding that he might be driven to give as much as he did in 2012 if he dislikes the Republican nominee enough. "After the primary, I may wind up saying, 'Let's do it.'"