"Jeremy Corbyn's numbers simply don't add up and he can't be trusted to run the economy or negotiate the right deal for Britain". While both parties were caught on the hoof by May's surprise decision to hold an early election, Labour had laid some of the ground work for an early election during the Conservative leadership contest last summer, when they expected that whoever prevailed in the race to succeed David Cameron would seek their own mandate.
"It will lead us through Brexit while putting the preservation of jobs first", he said, appearing in front of Labour's election manifesto: "For the many, not the few". It suggested that voters' impression of Labour in marginal seats improved when questions prompted them to think about their local area and their sitting MP rather than about the national campaign - implying that a visit from the national party leader might not necessarily be beneficial to Labour's vote.
Asked about the 45p rate for £80,000 earners by Jeremy Vine on BBC Radio 2, he said: "I'm not saying how much they are going to actually have to pay straight away, we will put it up during the parliament".
Will they succeed? It helps that the Conservatives did very little to prepare for an early election a year ago, and all but a trusted few discovered that May was holding an early election at the same time.
Leaders' visits can have an positive effect on the party's vote share, according to a study that examined the 2010 general election.
The poll follows Labour's manifesto launch in which it laid out plans to nationalise industries. A YouGov poll on May 12 said 31 per cent would vote Labour.
Mr Corbyn's allies believe he is likely to be able to stay in office should he win more than the 30.4 per cent share of the vote which Ed Miliband achieved in the 2015 election.
Britain, Mr. Corbyn said at his manifesto announcement at the University of Bradford, had been "run for the rich, the elite and the vested interests", adding: "They have benefited from tax cuts and bumper salaries while millions have struggled".
Labour spending plans would open up a £58 billion "black hole" in the public finances, leading to higher taxes and more debt borrowing, the Conservatives have warned.
Some Labour moderates fear that Mr Corbyn could use the findings as a way of clinging to power even if the party loses the election.