LONDON — Britain's Labour Party chose as its new leader Keir Starmer, a knighted former criminal prosecutor and moderate socialist, who replaces the more left-leaning Jeremy Corbyn after a crushing loss to Conservatives in elections four months ago.

Starmer won in a landslide Saturday, taking 56 percent of the 490,000 ballots in the first round, defeating second-place finisher and hard-left Corbynite Rebecca Long-Bailey, who took 28 percent.

The votes were cast by party members, registered Labour supporters and trade unionists, and together they signaled a desire for unity and moderation. Under Corbyn, Labour was beset by factionalism and purges, with the hard-left wing seeking to cleanse the party leadership of any remnants of former prime minister Tony Blair and his centrist New Labour movement.

Starmer, 57, will now serve as leader of the opposition in parliament, tasked with questioning Prime Minister Boris Johnson in the House of Commons in weekly bouts of oratorial combat.

Starmer could be a formidable voice for Labour in the verbal jousts. A former human rights lawyer, Starmer holds a law degree from Oxford and has a reputation as a skilled debater with a forensic eye.

He is not as flashy nor as funny as Johnson can be, nor as bombastic. But he is a well-briefed inquisitor. Starmer — whose mother was a nurse and father a toolmaker — is less known for withering put-downs, but more dogged in his pursuit of answers.

Starmer was knighted by the queen and became Sir Keir in 2014 for “services to law and criminal justice.” While he prefers to highlight his working-class roots, he is often referred to as Sir Keir in introductions and by the BBC — though not so much at Labour gatherings.

The baton was passed to Starmer as all politics now are viewed through the lens of the coronavirus fight. The Labour candidates campaigned recently not in person, but via email and video conference.

Johnson’s government — though criticized for getting a slow start, and failing to ramp up testing — is getting generally good marks from the public for its response to the spread of covid-19.

Starmer will have a tough job as opposition leader, having to prod the government to do more, faster and better, while not engaging in “opposition for opposition’s sake,” as the new Labour leader himself put it on Saturday.

The new politics of covid-19 in Britain may see voters want politicians to pull together, rather than score points in debates.

So far, Starmer and the opposition have focused their rhetorical fire on the government for failing to provide personal protective equipment for front-line health-care workers and to quickly offer widespread testing. They have also criticized Johnson’s team for bungling a chance to work with the European Union to purchase desperately needed ventilators from abroad.

Usually, the fight to succeed Corbyn would have dominated the news here.

Now? Not so much. On Saturday, Britain had more than 41,900 confirmed coronavirus cases and at least 4,300 deaths.

As the London Times cast the Labour contest in a headline: “What do you do when you reach the pinnacle of your political career, becoming leader of your party, and nobody cares?”

The party vote came after Corbyn resigned as leader following the December election, which saw Boris Johnson and his Conservative Party trounce Labour — even in its working-class strongholds in the faded industrial heartlands in the north of England.

Under Corbyn, Labour suffered its worst electoral defeat since 1935. But Starmer was also responsible. He was a top campaigner and leader of Labour and supporter of the party manifesto, which called to nationalize rail, mail, water and power generation — policies which Starmer said he still supports.

Parts of the 2019 manifesto — free Internet, improving troubled rail service, more money for schools and senior citizens and a sweeping Green New Deal to slow climate change — were popular proposals, according to opinion surveys.

But Corbyn was a deeply unpopular messenger. Corbyn said Labour had “won the argument” but lost the election to the Johnson’s Conservatives because of Britain’s difficult and delayed exit from the European Union.

The prime minister campaigned under a banner of “Get Brexit Done.” Corbyn and Labour had a more nuanced — or muddled — position of staging a second referendum with an up-down vote on whether to take the better deal Corbyn said he could negotiate with Brussels.

Under Corbyn, Labour also struggled with anti-Semitism in its ranks, with vulgar posts and taunts against Jews. “Anti-Semitism has been a stain on our party,” Starmer said. “And I will tear out this poison by its roots and judge success by the return of Jewish members and those who felt that they could no longer support us.”

On Saturday, in his video message, Starmer said Labour was the political movement that had created the National Health Service and the welfare state, which built hospitals and schools, protected minorities, opened up the universities and brought peace to Northern Ireland.

“But we’ve just lost four elections in a row. We’re failing in our historic purpose,” Starmer conceded. “Be in no doubt I understand the scale of the task, the gravity of the position that we’re in. We’ve got a mountain to climb.”

Starmer pledged to work with the government to save lives during the pandemic.

On Saturday, Johnson invited the opposition to join cross-party talks to “work together” on the crisis. Johnson is suffering from a fever and is moving into his second week of self-isolation after becoming infected by the coronavirus.

“This virus has exposed the fragility of our society. It’s lifted a curtain,” Starmer said. “We can see so clearly now who the key workers really are. When we get through this it’ll be because of our NHS staff, our care workers, our ambulance drivers, our emergency services, our cleaners, our porters.

“It will be because of the hard work and bravery of every key worker as they took on this virus and kept our country going.”

He said, “For too long they’ve been taken for granted and poorly paid. They were last and now they should be first.”