Why Sunak Faces One of His Toughest Weeks as U.K. Leader

Prime Minister Rishi Sunak of Britain embarked on one of the most politically fraught weeks of his tenure on Monday, facing a mutiny against his flagship immigration policy and testifying before an official inquiry into the coronavirus pandemic.

On a day of split-screen drama in the capital, Mr. Sunak expressed sorrow for Britain’s heavy death toll from Covid-19, saying, “It’s important that we learn the lessons so we can be better prepared in the future.”

But he was careful not to criticize his predecessor, Boris Johnson, whom he had served under as chancellor of the Exchequer during the crisis, and who came under intensive questioning last week over his own much-faulted performance during the pandemic.

While Mr. Sunak was defending his role in the government’s frantic Covid response, right-wing Conservative lawmakers were meeting a few blocks away to debate his revised policy of putting illegal immigrants on one-way flights to Rwanda. The legislation has fractured the party, alienating both Tory centrists, who worry that it goes too far, and right-wingers, who contend it does not go far enough.

With a parliamentary vote on the legislation scheduled for Tuesday, Mr. Sunak faces the possibility of a rebellion that could torpedo the Rwanda policy. If lawmakers pass the plan, it could still face a string of amendments, as well as a hostile reception in the House of Lords, the unelected upper chamber of Parliament.

For Mr. Sunak, it adds up to a devilishly difficult few days. He is under scrutiny for both his conduct as chancellor, when he repeatedly warned of the economic damage caused by lockdowns, and his skills as party leader, trying to salvage an immigration policy that has been struck down by Britain’s top court.

Mr. Sunak did his best to lower the temperature at the Covid hearing. He pushed back on suggestions from the inquiry’s chief counsel, Hugo Keith, that there were clashes between him and Mr. Johnson or other cabinet ministers over whether to impose lockdowns at several moments during the pandemic.

“I don’t think I ever referred to it as a clash,” Mr. Sunak said of the internal debates over Covid policies. “It’s right that there was vigorous debate, as these were incredibly consequential decisions for tens of millions of people.”