FILE - In this March 20,2018, file photo, House Speaker Paul Ryan of Wis., pauses as he speaks to reporters on Capitol Hill in Washington. Ryan's political future as House speaker has been such a topic of speculation that even the simple question of whether he will seek re-election to his Wisconsin seat remains secret.  (AP Photo/J. Scott Applewhite, File)
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FILE - In this March 20,2018, file photo, House Speaker Paul Ryan of Wis., pauses as he speaks to reporters on Capitol Hill in Washington. Ryan's political future as House speaker has been such a topic of speculation that even the simple question of whether he will seek re-election to his Wisconsin seat remains secret. (AP Photo/J. Scott Applewhite, File)
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(CNN) —  

House Speaker Paul Ryan’s retirement has dealt a morale-bruising blow to Republicans’ hopes of holding onto their majority in the chamber in this year’s midterm elections.

Ryan’s surprise Wednesday morning announcement that he won’t seek re-election could rattle GOP incumbents and donors just seven months before November’s contests, GOP lawmakers and operatives said.

The two most pressing concerns for Republicans: They are losing their leading fundraiser, potentially creating a major financial void, and more lawmakers could follow Ryan’s lead and head for the exits.

“It may encourage other Republicans to not run again, I think more so than affecting the money,” said Rep. Thomas Massie, R-Kentucky. “We’ve already got twice as many retirements in our party as the Democrats. This may be a signal that it’s OK to retire.”

The party is defending its 23-seat House majority against an energized Democratic base that sees the House as its best chance to put a check on President Donald Trump.

Ryan wasn’t the only retirement Wednesday. Florida Rep. Dennis Ross, first elected in the tea party wave of 2010, also announced he won’t seek re-election this fall. That brings the total number of Republicans leaving or having left the House this cycle to 41.

Ryan isn’t likely to disappear from the political landscape immediately.

He was speaking to major donors on a conference call Wednesday, and according to an invite, he planned to say he would continue raising money and campaigning for House Republicans through the remainder of 2018.

Rep. Ryan Costello, R-Pennsylvania, told reporters on Wednesday that Ryan said in a morning meeting of House Republicans that he was going to “run through the tape through the end of the year to help elect Republicans.”

Asked whether this was a bad sign for GOP control of the House, he said: “Others may try and spin it that way, but I don’t see it that way.” He called retirements a “a decision-by-decision basis.”

Ryan has personally raised more than $40 million for the House GOP’s campaign arm in the 2018 election cycle. Though Ryan’s effectiveness as a lame-duck fundraiser isn’t yet clear, Republicans hope the leadership race that’s likely to develop between California Rep. Kevin McCarthy, an adept fundraiser himself who has raised money with Vice President Mike Pence for the party, and Louisiana Rep. Steve Scalise will allow the two to fill the gap.

The National Republican Congressional Committee has already raised $115 million for the cycle. The Congressional Leadership Fund, a super PAC that backs House GOP candidates and is closely aligned with Ryan, could be more important to watch.

The Wednesday retirements were the latest in a series of damaging developments for the GOP this year.

In February, the Pennsylvania Supreme Court struck down the state’s gerrymandered congressional map and ordered new district lines in place for November. The redrawn map makes several seats more difficult for the GOP to hold.

In March, Democrat Conor Lamb won a special election for a House seat in western Pennsylvania that Trump had carried by 20 percentage points in 2016.

And earlier this month, the Democratic-backed candidate easily won a state Supreme Court seat in Wisconsin, a statewide victory that offered further evidence of a big swing from 2016 to 2018.

Republicans face more tests before November. They’ll try to hold onto former Rep. Trent Franks’ House seat in Arizona in an April 24 special election, and then will attempt to keep former Ohio Rep. Pat Tiberi’s seat in an August special election.

CNN’s Juana Summers contributed to this report.