None took that opportunity more ruthlessly than the foreign secretary, Boris Johnson, who has made two interventions undermining Mrs. May’s strategy for negotiating Britain’s withdrawal from the European Union, known as Brexit.

(Mr. Johnson created a contretemps as well, telling a conference panel that the Libyan coastal city of Surt, a former redoubt of the Islamic State terrorist group, could be “the next Dubai” if the authorities “could just clear the dead bodies away.” Critics, including some members of the party, said he should resign.)

While there seems to be no immediate plot to unseat Mrs. May, analysts say that the longest she can expect to remain in her job is until March 2019, when the withdrawal is to take place. The party conference, and this speech in particular, was an opportunity to reassert her authority over a cabinet squabbling over the details of Brexit.

That was not how it turned out. “Before the speech, most people would have bet on her coming out of the conference season alive, although the sharks were already circling,” said Tim Bale, professor of politics at Queen Mary, University of London, referring to potential rivals for Mrs. May’s job.

“The speech has put blood in the water,” he said.

On Wednesday, Mrs. May promised that more affordable homes would be built to address the country’s housing crisis. She detailed a cap on energy prices and promised to create a British version of the American dream.

She also apologized to Conservative Party members for having led an election campaign that was “too scripted, too presidential,” and spoke only briefly about the divisive issue of Brexit.