Then U.S. President Donald Trump threw a curve ball into the campaign, popping up on a U.K. talk radio show Thursday to slam Corbyn and urge Conservative Prime Minister Boris Johnson to join forces with arch-Brexiteer and political rival, Nigel Farage.
Tossing aside the convention that foreign leaders shouldn't intervene in other countries' domestic politics, Trump told Farage on the British politician's own radio show that Corbyn would "be so bad for your country ... he'd take you into such bad places."
It was a surreal detour to a six-week campaign that won't even officially begin until next week. All seats in the 650-seat House of Commons are up for grabs in the early election, chosen by Britain's 46 million eligible voters.
Corbyn, in his first stump speech, declared that his left-of-center party's plan would take on "vested interests" and "born to rule" elites — a dig at Johnson and his Conservative party's big-business backers.
"We're going after the tax dodgers. We're going after the dodgy landlords. We're going after the bad bosses. We're going after the big polluters. Because we know whose side we're on," Corbyn told supporters at a rally in London. "Whose side are you on?"
Johnson sought this election, which is being held more than two years early, to break the political impasse over Britain's stalled departure from the European Union. He plans to campaign as the Brexit champion, blaming Corbyn's "dither and delay" for the country's failure to leave the EU on Thursday as scheduled.
While the Conservatives have a wide lead in most opinion polls, analysts say the election is unpredictable because Brexit cuts across traditional party loyalties. Corbyn wants to shift the election battleground away from Brexit and onto more comfortable terrain: the many versus the few. Labour is hoping that voters want to talk about issues such as health care, the environment and social welfare — all of which saw years of funding cuts by Conservative governments — instead of more Brexit debates.
Corbyn, a fierce critic of Trump, likely won't mind the U.S. president's intrusion but Johnson could be a different story. Speaking to Farage on radio station LBC, Trump slammed Corbyn and praised Johnson as "a fantastic man" — but urged Britain's Conservative leader to make an electoral pact with Farage's Brexit Party.
"I'd like to see you and Boris get together, because you would really have some numbers," Trump told Farage, the president's leading champion in Britain. "I know that you and him will end up doing something that could be terrific if you and he get together as, you know, an unstoppable force," Trump added.
Yet Trump also claimed that "certain aspects" of Johnson's EU divorce agreement would make it impossible for Britain to do a trade deal with the U.S. Johnson has already ruled out any electoral pact with Farage's Brexit Party, which wants to leave the EU without a deal on future relations and is vying with the Conservatives for Brexit-backing voters.
On the other side of the divide, the centrist Liberal Democrats, who want to cancel Brexit, are wooing pro-EU supporters from both the Conservatives and Labour in Britain's big cities and liberal university towns.
Sticking to his party's core issues, Corbyn on Thursday called out prominent business leaders — including media mogul Rupert Murdoch and aristocratic landowner the Duke of Westminster — as he painted Johnson's Conservatives as champions of the wealthy few.
Johnson once again banged the Brexit drum, ignoring his failure to get British lawmakers to pass his Brexit divorce deal and his previous vow to leave the EU by Oct. 31 "come what may." Earlier this week, the EU granted Britain a three-month Brexit delay, setting a new Jan. 31 deadline for the country to leave and imploring British politicians to use the extra time wisely.
"If you vote for us and we get our program through ... we can be out at the absolute latest by January next year," Johnson said Thursday as he visited a hospital. Johnson is also trying to steal some of Labour's thunder by promising more money for key public services such as hospitals, police and schools.
Labour is vulnerable over Brexit because the party is split. Some of its leaders, including Corbyn, are determined to go through with British voters' decision to leave the EU, while others want to remain. After much internal wrangling, Labour now says if it wins the election, it will negotiate a better Brexit divorce deal, then call a referendum that gives voters a choice between that deal and remaining in the EU. The party has not said which side it would support.
"Labour will get Brexit sorted within six months. We'll let the people decide whether to leave with a sensible deal or remain," Corbyn said. Corbyn shrugged off suggestions that he is dragging down the party's popularity. Critics say the 70-year-old socialist is wedded to archaic policies of nationalization and high taxes, and accuse him of failing to stamp out anti-Semitism within the party.
"It's not about me," Corbyn said Thursday. "It's not a presidential election. It is about each and every one of us (candidates)." Johnson's critics bash the 55-year-old for his long history of misrepresentations and broken promises, and a string of offensive comments that he has tried to shrug off as jokes.
More than three years after the Brexit referendum, Brexit positions have become entrenched and the debate has soured, with lawmakers on all sides receiving regular abuse online. The toxic political atmosphere has prompted some long-time lawmakers to drop out of the race, including Culture Secretary Nicky Morgan.
"Over the last couple of years, I have had to have a couple of people prosecuted for death threats," Morgan said. "We've got to tackle this culture of abuse."
An earlier version corrected the spelling of Corbyn in first sentence.
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