WASHINGTON — The leading super PAC backing Hillary Clinton, Priorities USA, reported Saturday it had nearly $40 million in cash on hand, a staggering amount less than three months away from Election Day.

The funds will be critical to turning out the vote in key states, as well as flooding the airwaves with anti-Donald Trump advertisements.

Priorities spokesman Justin Barasky said the group has raised $153 million so far, with more than $9 million raised in July.

One Democratic donor in particular is reasserting himself as a heavyweight: billionaire environmentalist Tom Steyer. Steyer gave another $7 million to his super PAC, NextGen Climate, last month, raising his total contributions to that group this cycle to over $35 million. The Clinton supporter struggled to impact the elections in 2012 and 2014, but he has continued his efforts in this election, with the stated goal of inspiring action on climate change.

Clinton is scheduled to attend a top-dollar fundraiser Tuesday at the Hollywood Hills home of Justin Timberlake and his wife, actress Jessica Biel, a source with knowledge of the fundraiser told CNN. Leonardo DiCaprio was supposed to host the event but pulled out due to a scheduling conflict.

The event comes as part of a three-day, eight-fundraiser-trip to California for Clinton.

Trump lagging behind

Trump’s main allied PACs are not currently on pace to keep up with Clinton’s. The main Trump group, Rebuilding America Now, is not scheduled to file a campaign finance report this weekend, though the group’s chief strategist, Ken McKay, told MSNBC this week it had raised more than $10 million this year.

A second Trump group, Great America PAC, raised only $2.4 million this month, much of it from small donors.

An anti-Clinton PAC, Defeat Crooked Hillay PAC, got $2 million more from Bob Mercer, a reclusive hedge-funder close to Trump’s new campaign leadership. But the PAC last month failed to secure any other major donations, hurting its claim that it is one of the primary Trump super PACs.

Meanwhile, former New York City Mayor Mike Bloomberg did some of his first 2016 spending by contributing $5 million to his super PAC, Independence USA.

Nearly $300 million spent between campaigns

As of the end of July, the Clinton campaign reported to the Federal Election Committee that it had raised almost $275 million and spent over $230 million. Over the same period, the Trump campaign had raised slightly over $91 million and spent just over $71 million. Not including outside groups, the two campaigns have combined to spend more than $300 million so far in this election cycle.

The Trump campaign just began its general election advertising efforts this weekend, an attempt to catch up in an area where the Clinton campaign has so far completely outspent the Republican nominee. The initial ad buy came around $4 million on Friday and was targeted at four swing states.

The Republican National Committee also announced Saturday it had raised $199.5 million this election cycle, including $27.2 million in July. The party currently has $34.5 million cash on hand, the RNC said in a statement.

The Democratic National Committee, meanwhile, has raised $151.3 million this cycle, pulling in $32.3 million last month and retaining $10.1 million cash on hand, the group said in a statement.