Priorities USA Action, the main super PAC backing Democratic presidential nominee Hillary Clinton, raised $21.7 million in August, its biggest money month yet.

The massive haul means the super PAC — which collected $79 million in 2012, when it was supporting the reelection of President Obama — has now amassed $132 million. It started September with $41.5 million in the bank.

The super PAC's financial success is largely due to a small group of wealthy Clinton allies who have been regularly doling out seven-figure checks. Together, the top six donors as of last month have given Priorities $43.5 million — a third of the money collected by the super PAC, campaign finance reports show.

Here are the biggest givers to Priorities last month and their overall totals:

Hedge fund founder Donald Sussman: $2 million in August/$13 million to date

Investor George Soros: $2.5 million/$9.5 million

SlimFast founder Daniel Abraham: $3 million/$9 million

Media company owner Fred Eychaner: $3 million/$8 million

Former hedge fund scientist Henry Laufer and his wife, Marsha: $2 million/$4 million

This elite cadre of donors are also helping subsidize the Democratic congressional super PACs. Of the $7.1 million raised in August by House Majority PAC, $3 million came from Eychaner and $2 million was from Sussman. In addition, Sussman gave $1 million last month to Senate Majority PAC.

Anu Narayanswamy contributed to this report.