Andrea Leadsom has said she is “actively considering” entering the race to replace Prime Minister Theresa May. (Daniel Leal-Olivas/AFP/Getty Images)

A day of fevered speculation about whether British Prime Minister Theresa May would resign concluded instead with the resignation of one of her key ministers, House of Commons leader Andrea Leadsom.

May appeared to be holding on, for the moment, amid growing calls for her to step aside and make way for a fresh leader who could break the current Brexit impasse.

But the defection of Leadsom was a blow to the prime minister.

Leadsom, a Brexit supporter, has repeatedly defended May’s Brexit deal in Parliament.

She is also a longtime rival of May’s. Leadsom and May were the two finalists in the 2016 contest to become leader of the Conservative Party and the next British prime minister. Leadsom withdrew from that race after a controversial interview in which she suggested being a mother made her a better pick than May, who doesn’t have children.

But she may be eyeing another run for No. 10. On Tuesday, Leadsom told LBC radio that she was “actively considering” and “preparing” for a leadership bid.

She would join a crowd of contenders from the Conservative Party who have indicated an interest in replacing May. Former foreign secretary Boris Johnson is currently leading in opinion polls.

In her resignation letter, Leadsom said she no longer believed May’s approach to Brexit could “deliver on the referendum result” or ensure “a truly sovereign United Kingdom.”

Leadsom said a second Brexit referendum would be “dangerously divisive.” May, too, has opposed a second referendum, but on Tuesday she offered Parliament a chance to vote on whether there should be a second public vote.

Leadsom added that tolerance for those in May’s leadership team “who advocate policies contrary to the government’s position had led to a complete breakdown of collective responsibility.”

A spokesman for Downing Street said May was “disappointed” that Leadsom had resigned, but added — defiantly — that the prime minister “remains focused on delivering the Brexit people voted for.”

There was much commotion on Wednesday over the possibility that May could be pushed out by lawmakers in her own party.

On Tuesday, May delivered what was potentially her last big sales pitch for her Brexit plan, urging lawmakers to pass a deal they’ve already rejected three times. May offered a few new tweaks, including the enticement of a vote on a second referendum. It went down like a lead balloon.

Even previously loyal Conservative lawmakers were suddenly popping up on telly or in newspapers saying that she had to go.

Tom Tugendhat, a Conservative lawmaker and chair of the foreign affairs committee, wrote in the Financial Times on Wednesday that “leadership matters; it has been absent for too long.” He said that May “deserves respect” but that a new leader was needed to “inject fresh energy into a moribund process and rebuild the trust necessary to deliver a deal.”

But May appeared to win a stay of execution, for a few days at least.