Senate Republicans' campaign arm raised more than $5 million last month, and has almost $27 million ready to help candidates, the Associated Press reported Saturday.
The National Republican Senatorial Committee fundraising summary shows it raised July fundraising efforts in 2010 and 2012, and has now raised about $76 million in 2014.
However, the committee has struggled to keep up with its Democratic rival, the AP reported.
The Democratic Senatorial Campaign Committee has outraised Republicans in 16 of the previous 18 months. By the end of June, it had raised $125 million and saved more than $30 million.
The Senate Democrats' committee has not yet released its July numbers, and has until Wednesday to do so.
There are close races in several states, including Kentucky, North Carolina and Iowa, and much of the party committees' budgets will go towards negative television ads, direct mail and phone calls.
In Kentucky, incumbent and Senate Minority Leader Mitch McConnellMitch McConnellThe Memo: Winners and losers from the battle over healthcare GOP senators pitch alternatives after House pulls ObamaCare repeal bill Under pressure, Dems hold back Gorsuch support MORE faces a challenge from Kentucky Secretary of State Allison Lundergan Grimes (D).
In North Carolina, Democratic incumbent Sen. Kay HaganKay HaganLinking repatriation to job creation Former Sen. Kay Hagan in ICU after being rushed to hospital GOP senator floats retiring over gridlock MORE is locked in a close race with state Rep. Thom Tillis (R).
In Iowa, Democratic Rep. Bruce BraleyBruce BraleyTen years later, House Dems reunite and look forward Trump: Ernst wanted 'more seasoning' before entertaining VP offer Criminal sentencing bill tests McConnell-Grassley relationship MORE is facing a challenge from state Sen. Joni Ernst (R).
Republicans will claim a majority in the Senate for the first time since 2006 if they pick up six seats.