Britain’s Conservative Party suffered the worst election defeat of its modern history less than three months ago. Yet one would be hard pressed to find much evidence of it at the party’s annual conference in Birmingham, where the drinks flowed, conversation crackled and the mood could be only described as light.

Unburdened by government, energized by a lively leadership contest and gleeful at the bumpy debut of Prime Minister Keir Starmer’s Labour government, the Conservatives gathered to plot their future, with some members expressing relief rather than frustration at being thrust into the opposition.

“I was expecting something a little more gloomy, seeing as we had been defeated,” said James Paterson, a party member from Hinckley, in the East Midlands. Instead, he said: “It’s really positive, it’s buzzing. The way the Labour Party have made such a mess of their first few months is making it easier.”

The upbeat atmosphere was a stark contrast to Labour’s conference last week, which was clouded by anxiety over news media reports about freebies accepted by Mr. Starmer and other senior Labour politicians, as well as the general weight of running the country after being out of government for 14 years.

Now taking their turn in opposition, the Conservatives are focusing on electing a new leader. The four remaining candidates — Kemi Badenoch, James Cleverly, Robert Jenrick and Tom Tugendhat — ran a beauty-contest-style gauntlet, giving interviews, grinning for selfies, lobbying lawmakers and even hawking branded merchandise from their own booths.