WASHINGTON — Fifteen months after Republicans took full control of Washington, the man once seen as central to the party’s upbeat and inclusive future is abandoning one of the most powerful jobs in the capital, imperiling the G.O.P. grip on the House and signaling that the political convulsions of the Trump era are upending the conservative movement.
House Speaker Paul D. Ryan’s retirement announcement on Wednesday blindsided many House Republican candidates and their campaign leaders who expected him to help them win the midterm elections in November. His decision to leave Congress at 48 also sent an undeniably pessimistic message to his party: That neither the House speaker nor President Trump has shown any real ability to bridge the internal tensions that have plagued congressional Republicans for years and made it difficult for the party to forge consensus on policy beyond the unifying issue of taxes.
But for House Republicans, and for a White House bracing for a potential Democratic impeachment inquiry, the more immediate and ominous impact of Mr. Ryan’s retirement was unmistakable: He has made it more difficult for his party to keep control of the House, where Republicans currently hold a 23-seat majority. With one decision, Mr. Ryan has turned an already difficult midterm election into a precarious task for his remaining colleagues.
“This is the nightmare scenario,” said former Representative Thomas M. Davis, a Virginia Republican. “Everybody figured he’d just hang in there till after the election.”
Mr. Ryan’s exit is a destabilizing blow to Republicans’ 2018 plans on nearly every front. He has been the party’s most important fund-raiser in the House, attending fund-raisers nearly every night he is in Washington and raising more than $54 million so far for this election. In contrast to a president who embraces chaos, Mr. Ryan has also been a reassuring figure for the business community and a source of perceived stability for restless lawmakers pondering retirement.
And Mr. Ryan has been the most important voice on the right calling for a campaign message focused on the economy and taxes, rather than the hard-right culture war issues Mr. Trump delights in stoking.
Mr. Ryan indicated to advisers that he knows retiring will create political difficulties for the party but that he felt he could not in good conscience commit to another full two-year term, according to two Republicans familiar with the conversations.
Yet his explanation is of little comfort to those Republicans on the ballot this year who were expecting Mr. Ryan to raise millions for and campaign with lawmakers across the country. Even though he vowed to colleagues on Wednesday that he would keep fulfilling those political responsibilities, he will not be nearly as big a draw at fund-raisers now that he is a lame duck.
Former Representative Thomas M. Reynolds of New York, a former chairman of the Republicans’ House campaign committee, said that Mr. Ryan had effectively scrambled the party’s fund-raising machinery and that other, lower-profile leaders would have to pick up the slack.
“It will be a difficult task for Paul to hold his strong, vibrant fund-raising,” Mr. Reynolds said. “When you’re a lame duck, it changes those dynamics.”
And with the candidate filing period still open in 19 states, Mr. Ryan has lost any real power to convince other wavering Republicans that they must run again.