Hedge funds are playing a far bigger role in 2016 than in past elections—and Hillary Clinton has been the single biggest beneficiary.

Owners and employees of hedge funds have made $122.7 million in campaign contributions this election cycle, according to the nonpartisan Center for Responsive Politics—more than twice what they gave in the entire 2012 cycle and nearly 14% of total money donated from all sources so far.

The lines around what constitutes a hedge fund aren’t always clear in the data, or in the financial industry. But the numbers are stark. OpenSecrets.org, the center’s website, says employees or owners of hedge funds and private-equity firms contributed $27.6 million to pro-Clinton groups or her campaign, according to federal data released in July. Counting contributions from similar private investment funds, the data show seven financial firms alone have generated $47.6 million for groups working on Mrs. Clinton’s behalf.

The total for Donald Trump: About $19,000.

Mr. Trump, of course, didn’t start actively soliciting campaign contributions until recently and even shunned outside political groups working on his behalf. Hedge-fund employees have contributed heavily to other Republican groups this cycle—$65.8 million ​so far—mainly in support of candidates who opposed Mr. Trump in the primaries. Some who had supported other Republican candidates are now beginning to give to pro-Trump groups.