Sixty mega-donors gave at least $100,000 each to a joint committee raising funds for Donald Trump and the Republican Party, together pouring in $15.4 million from late May until the end of June, new campaign finance records show.

The huge sums that flowed into the Trump Victory fund made up 30 percent of the $52.3 million that the presumptive Republican nominee raised overall in conjunction with the party over the five-week period, his largest fundraising haul yet.

Trump’s efforts got a major lift from a small group of wealthy donors who contributed as much as $449,400 each to Trump Victory, the biggest amount ever solicited by such a committee. Such super-sized checks are now possible thanks to a 2014 Supreme Court decision, along with a measure tucked into a spending bill later that year that loosened party fundraising rules.

Trump’s first round of fundraising in conjunction with the Republican National Committee shows how lucrative it is to turn to the uber-rich for support. But it also illustrates how dependent it makes the real estate developer on the party, which gets to pocket the lion’s share of the big-money contributions.

Thirteen supporters gave Trump Victory the $449,400 maximum.

Most of the money they donate is allotted for the RNC, which received a $10.1 million transfer from the committee. But not all of that money can be used freely. More than $4 million was earmarked for the party’s convention and legal accounts – funds that cannot be used to pay for the RNC’s political efforts on the ground.

Trump Victory raised $25.7 million in all during the second quarter of the year, while a second joint fundraising committee called Trump Make America Great Again brought in $6.7 million, new campaign finance filings show. The Trump campaign, which can only accept donations up to $5,400 per person, announced earlier this month that it had brought in $19.9 million in direct donations in June, while Trump personally contributed another $3.8 million. Trump Victory transferred $2.2 million to the campaign, meaning his committee brought in a total of roughly $26 million in June.

That still falls short of the $40.5 million that Democratic contender Hillary Clinton raised for her campaign in June.