Washington (CNN) - The latest round of campaign committee disclosures show political action committees and outside groups spent tens of millions of dollars last month, entering the home stretch of the 2018 midterm elections.
Official party committees and a collection of super PACs closely affiliated with congressional leadership led the efforts, according to the new Federal Election Commission reports, filed late last week.
At the top of the list was the National Republican Senatorial Committee, which spent more than $18.2 million last month amid the tightening battle for control of the upper chamber of Congress, per FEC filings. Over $12.6 million of NRSC spending went toward independent expenditures targeting critical Senate contests in Missouri, North Dakota, Montana, Nevada and West Virginia.
The Democratic Congressional Campaign Committee was the second biggest spender in August, coming in just behind the NRSC with over $18.1 million in spending. The DCCC made $8.1 million worth of independent expenditures in the month, spread across a series of key House races in Arizona, California, Florida, Iowa, Kansas, New York, Minnesota, Virginia and Washington.
The Republican National Committee came in third, spending $16.5 million. Its only major independent expenditures, a little over $600,000, went toward the special election in Ohio's 12th Congressional District in early August between Republican Troy Balderson, the winner, and Democrat Danny O'Connor.
In fourth, with more than $12.3 million of spending, was Senate Majority PAC, the leading Democratic super PAC targeting US Senate races. Tom Steyer's advocacy group, NextGen Climate Action, was next with $9.4 million, followed by the National Republican Campaign Committee with $9.1 million and the Democratic National Committee with $8.9 million.
A trio of super PACs -- Senate Leadership Fund ($7.7 million), House Majority PAC ($6.3 million) and Women Vote! ($5.5 million) -- rounded out the top 10.
Congressional Leadership Fund, a top GOP super PAC affiliated with House Republican leadership, files quarterly reports rather than monthly reports, and as such could not be included on the list -- but according election-specific filings, the group spent about $16 million between July 19 and August 27.
Who got the most
When it came to fundraising, Democratic committees and associated groups also dominated August.
Senate Majority PAC, among the top spenders, clocked in at No. 1, raising nearly $18 million last month.
Close on its heels were three other key Democratic groups -- House Majority PAC, the DCCC and NextGen Climate Action Committee -- all of which hauled in eight-figure sums.
The only Republican group in the top five was the RNC, at the No. 2 slot. It raised just shy of $16.5 million for the period (although the RNC does have one of the highest war chests of cash on hand, at nearly $42 million).
The DNC posted one of its stronger fundraising months of the cycle, raising $9.2 million -- the eighth largest haul. But the group's broader financial outlook remained troubled, as the committee reported having over $7 million remaining in debt and just $7.9 million in cash on hand.
Who gave the most
The robust August fundraising totals were driven largely by a small group of wealthy donors who combined to give over $26.8 million in the month.
At the top of the list: Amazon founder and Washington Post owner Jeff Bezos, who gave $10 million to the With Honor Fund, a nonpartisan super PAC dedicated to supporting campaigns by military veterans. With that huge contribution, Bezos ended up giving more than twice as any other donor in August.
In second place was Fred Eychaner, a Chicago philanthropist and a leading Democratic donor, who gave $4 million to the Senate Majority PAC.
Michael Bloomberg -- who has pledged to spend up to $80 million on the midterms -- was the third largest donor of the month, giving about $3.5 million between Women Vote!, a super PAC affiliated with Emily's List, and his own PAC, Independence USA PAC.
Also among the top 10: Stephen Schwarzman and George Soros, mainstays of the Republican and Democratic fundraising circuits, respectively, as well as Richard Uihlein, a Midwestern shipping magnate who has emerged as one of the top Republican donors of the 2018 cycle so far. TV host Bill Maher also made the list with a $1 million contribution to Senate Majority PAC.