Once it became apparent the party had not only avoided electoral annihilation but actually gained 30-odd seats, there were those who read his fudge as a cunning ploy to attract Labour voters on both sides of the Brexit argument.
Cunning no more. In one fell swoop the leader of the opposition has revealed not only that he does not understand how the European Union works, but also how out of touch he is with Labour voters, donors and his own MPs.
First Corbyn signalled his desire to leave the Single Market on the mistaken assumption that it comes necessarily from leaving the EU. A number of his own MPs lined up to correct him, but no clarification was issued.
Then the conspicuousness of his position was further underscored by Welsh First Minister Carwyn Jones’ insistence that leaving the Single Market would be bad news for farmers and jobs. Once again, Labour MPs lined up to side against Corbyn.
As our story today details, trade unions such as the TUC and Unite also want to remain in the Single Market for job security.
Meanwhile, a recent opinion poll suggested almost eight out of 10 Labour voters want to stay in the Single Market.
Corbyn may have played a difficult hand well during the election, but he’s starting to badly fumble now. His apparent enthusiasm for a hard Brexit is increasingly obvious, and at odds with the views of much of his party, its voters, and even its mass of new Corbynite supporters.
Many young Corbyn-backers admire his 70s-style socialist rhetoric, but few of the younger generation see EU integration as a Thatcherite ploy, in the way that Corbyn and his left-hand man John McDonnell have done for several decades.
Alongside his U-turn on student debt, could Corbyn’s stance on Brexit start to weaken his youthful supporter base and erode the party’s gains in the polls? The Labour leader may have been riding high since 8 June, but as he should know by now, in politics the tide can turn scarily quickly.