Congresswoman Marjorie Taylor Greene’s planned departure from the House of Representatives creates a real crisis for Speaker Mike Johnson. With more than a year to go until a new Congress is inaugurated in January 2027, Mr. Johnson’s majority may not just becoming inoperative — it is at risk of disappearing altogether. 

Ms. Greene’s criticism that the Republican majorities in Congress have been “sidelined” by the executive branch is a gripe several senior members of the House have quietly had for months, especially those Republican appropriators who decide how to spend federal dollars, only to see those funds slashed unilaterally by the White House. 

With their seven-week vacation behind them, Republicans have also lost meaningful time in pursuing other legislative priorities, including health care reforms, regulation of artificial intelligence, and other pet projects for members. 

“We endured an 8 week shut down wrongly resulting in the House not working for the entire time, and we are entering campaign season which means all courage leaves and only safe campaign re-election mode is turned on,” Ms. Greene wrote in her letter announcing her resignation last week. 

The ability to do legislative work could become much harder once Ms. Greene departs Washington, however. 

The House majority currently stands at 219 Republicans to 213 Democrats. Two deep-blue seats — one in New Jersey and one in Texas — will be filled in the coming months after Congresswoman Mikie Sherrill was elected New Jersey governor and Congressman Sylvester Turner of Houston passed away. 

That will ensure a 219-seat Republican majority to a 215-seat Democratic minority. Once Ms. Greene departs, that GOP majority will fall to only 218 members. 

Much of Mr. Johnson’s political future currently lies in the suburbs just west of Nashville in middle Tennessee, where voters will go to the polls next week to elect their new member of Congress. The previous lawmaker, Congressman Mark Green, resigned over the summer to pursue other career opportunities. 

The district — Tennessee’s seventh congressional district — is blood red, considering Mr. Trump won it by more than 20 points last year. Democrats and Republicans alike, however, believe that the Democratic Party could pull off a surprising win. 

State representative Aftyn Behn, the Democratic nominee, has raised $1.2 million for the race, while the GOP candidate, Matt Van Epps, raised just under $1 million. Outside groups have spent much more, however, with $4 million having poured into the district in recent months — a sign that both parties believe this race is competitive. 

If Democrats can pull off an improbable win there on December 2, the House Democratic minority will climb to 216 members. Once Ms. Greene’s seat is filled by next spring, the House composition could sit at 219 Republicans to 216 Democrats. 

On party-line votes, Mr. Johnson would then be able to lose only one single member if he wants legislation to pass. 

But even that assumes that everything else remains static. As we have seen in the last 18 months, members of Congress — who skew far older than most other professions — have a predilection for dying in office. The average lifespan of an American is just about 76 years. Unfortunately for Mr. Johnson, he has 11 Republican colleagues who are either that age or higher. 

That possibility does not even consider Republican lawmakers simply getting sick of their jobs. On Monday morning, after Ms. Greene torched Congress as an irrelevant branch of government, Punchbowl News reported that one House Republican privately agreed with Ms. Greene’s assessment, saying that the White House has shown no respect for the legislative branch. 

One lawmaker, Congressman Warren Davidson of Ohio, then decided to comment on the possibility of other GOP lawmakers quitting the House altogether, even before next year’s midterm elections. Mr. Davidson wrote on X that it was “highly plausible” that his colleagues may quit in the coming months as the legislative branch becomes less relevant.

If such a change in majority were to occur — which, to be sure, is not overwhelmingly likely at this point — then it would mark the first time in nearly 100 years that control of the U.S. House changed in between elections. Control of the Senate most recently flipped in 2001, when Republican Vermont Senator Jim Jeffords left his party to become an independent and caucus with the Democrats. 

The last time that the House changed hands in between elections, it was a series of deaths that ended the narrow House GOP majority — one even thinner than the majority Mr. Johnson has now. In 1931, the Republicans held a one-seat majority in the House, though a number of GOP lawmakers died before they were seated in December of that year, handing Democrats a bare majority.