Two prominent outside groups aligned with Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) combined to raise $66 million in 2017, record hauls that Republicans will need as they seek to maintain a majority in the House amid stiff political headwinds.

The Congressional Leadership Fund (CLF), which raised less than $500,000 in the last off-year, pulled in $26 million in 2017 and has $15 million in cash-on-hand. An affiliated group, the American Action Network (AAN), brought in another $40 million.

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“CLF’s record-setting off-year fundraising is a testament to Speaker Ryan’s leadership and House Republicans’ conservative agenda,” CLF and AAN Executive Director Corry Bliss said in a statement. “Knowing history is against us, CLF’s field program has laid the groundwork to protect the Republican House majority well ahead of Election Day, opening 27 field offices and making over 5 million voter contacts to date. AAN is well-prepared to continue to promote the conservative policies of House leadership, and CLF is ready to ensure Republicans maintain the majority in 2018.”

The party that controls the White House has historically struggled to maintain seats in Congress in midterm elections.

Democrats need to pick up 24 seats to take control of the House in 2018 and President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE’s low approval rating, coupled with the Democrats’ double-digit lead in generic ballot polling, has some predicting a wave election in which Republicans could lose the House.

The GOP’s efforts to hold on to the House have been complicated by a string of retirements. On Monday, House Foreign Affairs Committee chairman Ed Royce Edward (Ed) Randall RoyceThe 'extraordinary rendition' of a US Presidential Medal of Freedom recipient, 'Hotel Rwanda' hero Gil Cisneros to face Young Kim in rematch of 2018 House race in California The most expensive congressional races of the last decade MORE (R-Calif.) became the eighth panel chairman to announce he would not seek reelection.

House Republicans will have to defend at least 30 open seats in 2018 due to retirements, resignations or lawmakers seeking other offices, while Democrats will only have to contend with about half as many open seats.

The CLF and AAN have been putting their money to use by setting up shop in competitive districts.

The groups have offices in more than two-dozen congressional districts that are currently held by Republicans and claim that staffers there have already made more than 5 million voter contacts in the last year.