Truss, addressing a crowd of Conservative activists and lawmakers at an announcement event in the capital, joked that the lengthy leadership race was "one of the longest job interviews in history."
Her victory means she will become the country’s third female leader, after Margaret Thatcher and Theresa May.
Johnson announced his resignation in July when six months of rolling scandals culminated in a critical mass of his own lawmakers’ abandoning him.
Most of Britain’s 67 million people had no say in Truss’ ascension. Instead, she was chosen by the party’s 180,000 members, who are 97% white; skew older, wealthy and male; and lean to the right of Britain’s political spectrum. Truss does not appear to be hugely popular in polls of the broader public, and she was not the top choice of her party’s lawmakers, but she was the favorite of its members.
The next general election might not be until early 2025; polls give the opposition Labour Party large leads over the Conservatives following the acrimony around Johnson’s fall.
Labour leader Keir Starmer congratulated Truss in a recorded video but added, “The change we need in Britain is not a change at the top of the Tory party,” referring to the Conservative Party by its centuries-old nickname.
Top of Truss’ priorities will be the country’s cost-of-living crisis: skyrocketing bills for food and energy (household electricity and gas bills are set to triple), fears of blackouts this winter and inflation that has sent real-terms wages falling. Millions of people may face the choice between heating their homes or feeding their families, while many small businesses say they will fold unless the government takes action.
Truss has promised to announce her plans on the issue this week. In her acceptance speech, she vowed tax cuts and said: "I will deliver on the energy crisis."
But tackling the crisis is doubly hard because her party is bitterly divided over what to do about it.
Johnson assembled a broad coalition that agreed on one issue — Brexit — said Anand Menon, the director of the U.K. in a Changing Europe think tank. That big tent covers lifelong middle-class Tories in the southern countryside, who may want a small state and lower taxes, to party newcomers from the traditionally Labour-voting north, who generally favor more investment in public services.
“The party is so divided on the only issue that matters to people now, and that’s going to be problematic,” Menon said. “The only issue that matters is the economy.”
Trying to unite those factions is Truss, a political chameleon who, supporters say, has been nimble and pragmatic enough to adapt her views and whom critics decry as opportunistic.
She was born in Oxford to a math professor father and a nurse mother whom she described as “left-wing.” As a student at Oxford University, she supported the centrist Liberal Democrats and advocated such positions as abolishing the monarchy and banning nuclear weapons.
After she switched to the Conservatives, she was elected to Parliament in 2010 following several unsuccessful attempts.
In 2016, she voted to remain in the E.U. in the Brexit referendum. That put her on the liberal — and losing — side of a political and cultural war that has raged ever since. However, she has since switched sides, often displaying the zeal of the convert that seems to have convinced the party faithful.