Mr Gething admitted he had not backed Mr Corbyn in the last two Labour leadership contests, but accepted the party had voted "decisively" for him to be its leader and candidate for prime minister.
Thanks to the unintentional sneak preview, there was little in the document that came as a surprise.
At the launch, Mr Corbyn said "clearly we are not going to freeze benefits" and the party later insisted that commitment was covered by its pledge of an extra £2bn for universal credit.
An Ipsos MORI survey for the Evening Standard gave Labour an eight point jump in popularity, while a YouGov poll for The Times gave Jeremy Corbyn's party a two-point boost.
If Labour ended up with just 200 MPs, it would likely hand the Conservative government a working majority of more than 80.
Other papers left the manifesto off their front pages, leading instead with the death of Moors Murderer Ian Brady.
Labour would lose 45 seats but win former Lib Dem leader Nick Clegg's Sheffield seat as minor compensation putting them on a post war low of 188.
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Critics say the move leftwards stirs memories of the party's 1983 manifesto, described then by a Labour lawmaker as "the longest suicide note in history" for helping the Conservatives, and some have questioned how the party can fund its program.
Chancellor of the Exchequer Philip Hammond said the financial "black hole" in Labour's manifesto would hurt "every single family" and showed Corbyn "can't be trusted to run the economy or negotiate the right deal for Britain".
Ms Dugdale will say: "In the face of some of the greatest challenges our country has ever faced, the choice at this election is being presented as one between a Scottish National Party with no programme to speak of and an emboldened Tory party that is pushing a hard Brexit at all costs".
Corbyn promised a Labour government would immediately guarantee the rights of European Union citizens in Britain and reject the threat of walking away from Brexit talks. F our in 10 Labour backers said they may switch parties before polling day, with a third of those to the Conservatives.
The BBK don sat down with the Labour party politician to discuss ways to engage young people with politics, following some Twitter interaction. I was elected by a very large number of members and supporters, ordinary people all over this country.
"His economic ideas are nonsensical, his views on national security indefensible and he'd make a total mess of the Brexit negotiations", chief secretary to the finance ministry, David Gauke, said in a statement.