To understand the political tsunami set off by the Alabama Senate primary on Tuesday, when Roy Moore, an anti-gay Christian fundamentalist who believes that Biblical law should supersede the Constitution, won the Republican nomination* for a Senate seat in a runoff election, consider the case of Senator Bob Corker.

Corker is a two-term Republican from Tennessee. He is up for reëlection next year, and has already raised six and a half million dollars. He’s only sixty-five years old, which is young in the geriatric U.S. Senate. He has one of the most coveted committee assignments in Congress: chairman of the Foreign Relations Committee, which, aside from making him one of the most influential voices on foreign policy, is also a perch that makes raising campaign funds enormously easy. Corker won his 2012 campaign by thirty-five points. Trump won the state last year by twenty-six points. In short, Corker is a senator at his professional peak.

And yet on Tuesday, the day that Moore defeated Luther Strange, the incumbent senator who was appointed to the job when Jeff Sessions left to become Attorney General, Corker announced that he was retiring. “When I ran for the Senate in 2006, I told people that I couldn’t imagine serving for more than two terms,” he said in a statement. “Understandably, as we have gained influence, that decision has become more difficult. But I have always been drawn to the citizen legislator model, and while I realize it is not for everyone, I believe with the kind of service I provide, it is the right one for me.”

Nobody really believed him. Corker, after Strange, seems to have been the second Senate casualty of this latest phase of the G.O.P. civil war. Even though there was no heavyweight Republican lined up to challenge him in a primary, Corker decided that the environment was too toxic. “That guy did not want to go through the house of pain,” a Republican who worked on the Moore race said. “He did not want to go through what Luther Strange went through.”

Expect a lot more Republican casualties, especially in the Senate.

While it’s dicey to read too much into one state’s special-election primary, there are a number of lessons from Alabama. The first is about Trump, who endorsed Strange even though his most solid supporters in the state rallied around Moore, a former chief justice of the state Supreme Court who was twice booted off the court for disobeying the law—once, in 2003, for refusing to remove a monument of the Ten Commandments, and again, in 2016, for directing the state’s judges to maintain a ban on same-sex marriage. The idea of having Roy Moore in the United States Senate was terrifying to Washington Republicans, and Mitch McConnell and others convinced Trump to back his opponents, first in an open primary and then in this week’s runoff.

Naturally, the race was billed as a test of Trump’s ability to persuade his own base. It didn’t work. The Republican consulting firm Firehouse Strategies, in a memo to clients, noted that there was no correlation between knowledge of Trump’s endorsement and support for Strange. In mid-May, sixty-four per cent of Alabama Republicans knew about Trump favoring Strange. By primary day, this week, eighty per cent knew about it. Over the same period, G.O.P. voter support for Strange didn’t budge. The firm’s takeaway for its Republican clients is that, “while Trump may be good at translating his supporters’ sentiments, he is unable to persuade them.”

Another memo, obtained by the Times, puts the lessons for the Republican Party over all in starker terms. Since 2010, the year that the Tea Party insurgency began rocking the G.O.P. establishment, the ability of incumbents in Washington to tame its right wing has ebbed and flowed. In 2010 and 2012, several subpar candidates making outlandish statements won Senate primaries, and probably cost the Republican Party control of the Senate. The Party regrouped and snuffed out similar unelectable challengers in 2014, when it won control of the Senate, and in 2016. But the post-2016 period has ushered in a new wave of insurrection.

“This year’s Alabama Senate special election shows that the 2014-16 playbook for winning Republican primaries needs to be recalibrated and improved” was the conclusion of the memo’s author, Steve Law, the head of the Senate Leadership Fund, which is essentially Mitch McConnell’s funding vehicle to protect his mainstream Republican Senate majority from being overtaken by the Trumpist right. Law argued that Republican voters were “still angry,” and that McConnell’s inability to get much done, especially the repeal of Obamacare, was “political poison” in the race.

Most interesting, the lesson for the G.O.P. establishment is that it has lost control of the Republican Party. Law writes that, in the minds of Republican voters, Obama, previously the face of the opposition, has been replaced by Paul Ryan and Mitch McConnell. “Opposition to Obama used to be a mainstay of Republican messaging,” he wrote. “In Alabama, Strange’s litigation against Obama’s executive actions would have been political gold a year ago. But with Obama out of the picture, our polling found the issue to be a middling vote-getter. Now the answer to what is wrong in Washington is the Republican Congress.”

Law, contrary to some others, sees Trump’s inability to translate his support to Strange as inconsequential, arguing that the Party’s base is now defined by its reverence for Trump. “No other person, group or issue has the gravitational pull on Republican primary voters that Donald Trump commands,” he notes, adding that “support for President Trump directly correlates with likelihood to vote.” Republicans, he says, are more likely to see themselves as Trump supporters than as Republican Party supporters. The single most fatal line of attack in a Republican primary, he suggests, is evidence that a candidate has been critical of Trump. It’s worth noting that, last month, Corker told local reporters in Tennessee, “The President has not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate in order to be successful”—remarks that Trump then attacked on Twitter.

Steve Bannon, Trump’s former political strategist, who backed Moore, is now plotting an expansive campaign to recruit challengers to Republican Senate incumbents, and is targeting some dozen races next year. Despite carrying the banner of nationalism and populism, Bannon is ideologically flexible. His first criterion for candidates is authenticity. (He obviously cared little about Moore’s anti-gay views.) But Bannon’s most important priority is the current G.O.P. leadership. When he was in the White House, Bannon believed that McConnell stymied Trump’s agenda and that, especially in the Senate, there was no constituency for the nationalist cause. So Bannon and his allies have made a decision about next year’s midterms: they will not back any candidate who agrees to support McConnell as Majority Leader.

*This post has been updated to clarify the nature of Roy Moore’s electoral victory.