The candidates sought to channel an icon of the right: Margaret Thatcher.

LONDON — When Rishi Sunak kicked off his campaign for leader of Britain’s Conservative Party and prime minister in July, his choice of venue — a tire shop in the market town of Grantham — felt almost inevitable.

Grantham is the birthplace of Margaret Thatcher, an icon of the right who looms large in every Conservative leader contest, but never more so than in these economically straitened times.

Mr. Sunak and his opponent, Liz Truss, have both competed to wrap themselves in the mantle of Thatcher, who was prime minister from 1979 to 1990. Each has cast themselves as the true heir to her free-market, low-tax, deregulatory revolution at home, and her robust defense of Western democracy abroad.

“We must be radical,” declared Mr. Sunak, who, like Ms. Truss, served in the government of Prime Minister Boris Johnson and is responsible for some of the economic policies he now proposes to sweep away. The agenda Mr. Sunak was championing, he told the party faithful, was “common-sense Thatcherism.”

But experts on Thatcher say the candidates have been cherry-picking the legacy of the woman known as the “Iron Lady,” emphasizing the crowd-pleasing elements while glossing over the less appetizing ones, like some tax increases in 1981, during the depths of a recession, at a time when she was determined to curb runaway inflation.