Owen Smith has suggested Labour might have won last month's general election if he had been party leader.
The shadow Northern Ireland secretary said he hoped Labour would have won the election under his leadership, having defied expectations to claim some 40% of the vote under Jeremy Corbyn.
Mr Smith unsuccessfully challenged Mr Corbyn for the party leadership last year.
Mr Smith was asked on Sky's Sophy Ridge on Sunday whether he would have done as well as Mr Corbyn in June's poll.
Mr Smith said: "I don't know, I hope so.
"I hope I might have even got us to win, but I can't know that, Sophy.
"Look, I think Jeremy has clearly galvanised young people in this country. We've seen that not just in the election, but since.
"I met people during the election who hadn't voted ever, certainly people who hadn't voted for a long while, who felt Jeremy was speaking to and for them and that Labour was speaking to and for them.
"I don't think any of us can argue with that and therefore I think he's earned the right to try and get Labour into power and earned the right to be out next prime minister."
Mr Smith has been brought back into the shadow cabinet by Mr Corbyn since the election.