Senate Majority Leader Mitch McConnell (R-Ky.), joined by fellow Republican senators, from left, John Barrasso (Wyo.), John Thune (S.D.) and Majority Whip John Cornyn (Tex.), meets with reporters after participating a closed-door strategy meeting on Capitol Hill in Washington on June 20, 2017. (J. Scott Applewhite/AP)

The big-money race for the Senate is heating up.

Groups aligned with Senate Majority Leader Mitch McConnell (R-Ky.) together raised $22.9 million in the second quarter of 2018 and entered the third quarter with nearly $44 million in cash on hand, according to figures provided by the groups and Federal Election Commission records filed Friday evening.

One of the McConnell-aligned organizations, One Nation, will launch a $16 million ad blitz in August aimed at five states that are key to maintaining the Senate Republican majority, according to the group.

On the Democrats' side, the super PAC working to elect Senate Democrats posted strong fundraising figures starting in the first quarter, and continued to show financial muscle. The group does not release its affiliated nonprofit’s fundraising figures, which are not reported publicly.

The super PAC, Senate Majority PAC, had about $13 million more in the bank by the end of June than its GOP counterpart, Senate Leadership Fund, FEC records show. Senate Majority PAC had $32.7 million in available cash and Senate Leadership Fund alone had $19.5 million, FEC filings show. 

“As the battleground map narrows, Senate Democrats continue to have the momentum this cycle,” J.B Poersch, president of Senate Majority PAC, said in a statement.

[Meet the wealthy donors pouring millions into the 2018 elections]

The major Democratic super PAC Priorities USA Action raised $2.8 million in June and had $9.3 million in available cash. Of that $2.8 million, $2 million came from the billionaire investor and liberal donor George Soros. Soros has contributed at least $9.2 million to outside groups so far in the 2018 cycle, according to an analysis by The Washington Post.

Some of the major donors to the Republican super PAC included Blackstone Group chief executive and co-founder Stephen Schwarzman, who gave $5 million to the Senate Leadership Fund. The New York investor has emerged as a major donor to President Trump since his election. The only major corporate donation to the super PAC came from Conoco Phillips, which gave $1 million.

The August ad buys totaling $16 million announced by McConnell-aligned groups will target Democratic incumbents in Missouri, Indiana and North Dakota; fight for the seat in Tennessee being vacated by Bob Corker (R); and defend one of the most vulnerable Senate Republicans this year: Dean Heller in Nevada.

“Leader McConnell has proven himself to be an invaluable asset when it comes to confirming yet another constitutional conservative to our nation’s highest court for decades to come,” Steven Law, president of the McConnell-aligned Senate Leadership Fund, said in a statement. “Donors realize this and it has sharpened their focus on the importance of Republicans holding the Senate this November.”

The Republican National Committee continued to post strong fundraising figures in June, raising nearly $14 million compared with nearly $8 million by its Democratic counterpart.

So far this cycle, the RNC raised nearly twice as much money as the Democratic National Committee and has nearly six times the available cash as the DNC. The RNC has raised $201.7 million this cycle, and the DNC has raised $105.8 million. The RNC reported $50.7 million in cash on hand at the end of June, and the DNC reported $9 million, with $6.3 million of debt.

[RNC enters summer 2018 with double the DNC’s monthly fundraising haul]

The RNC reported spending $369,000 at Trump properties, the majority of that at the Trump National Doral Miami, bringing to $1.5 million the total spent at Trump properties since November 2016.