Jeremy Corbyn becoming prime minister is no longer impossible, the last Labour politician to be in charge of Scotland has said.
Jack McConnell was first minister for five years at Holyrood, before being ousted when the SNP came power in 2007.
At one point he had believed it was "very, very unlikely" that veteran left-winger Mr Corbyn could enter Downing Street - but while Lord McConnell said this was now possible, he doubted whether Labour now would be as transformative in power as Tony Blair was two decades ago.
Asked if Mr Corbyn would ever be prime minister, the former Scottish Labour leader told BBC Radio Scotland: "I no longer think that that is impossible."
He added: "I did think at one point it was very, very unlikely."
Lord McConnell, speaking on the Stephen Jardine programme, said politics was going through "incredible times", with a trend for leaders to be younger seemingly having been reversed.
"You would have said three years ago we were on a trajectory where every single political leader everywhere was getting younger and younger and younger, and where was that going to stop.
"We now have at the top of Britain's three political parties three of the oldest people to lead those parties in modern times."
Mr Corbyn, the leader of the Labour Party, is aged 68, while Conservative Prime Minister Theresa May is 60 and Vince Cable, the new UK Liberal Democrat leader, is 74.
While Lord McConnell said he would "certainly prefer" Mr Corbyn to be prime minister over the other party leaders, he raised concerns about causes the Labour leader had been involved with in previous years.
"I worry about some of the things he has promoted in the past, it will be interesting to see whether the responsibilities of leadership change his approach to places like Venezuela for example," he said.
"I worry about some of the stuff he has promoted in the past but I worry about the other options."
He continued: "I think we are in a very challenging, difficult place right now and I don't see a vision for the future that is based on a combination of social justice on one side and modernisation and being part of the 21st century on the other.
"I don't see that coming through in any party."
Recalling when Mr Blair came to power, Lord McConnell said: "People forget what a state Britain was in in 1997, whatever people think about Tony Blair and some of the decisions he made in office, the changes that took place after 1997 transformed this country.
"And if there is going to be a Labour government again I want to see it doing those kind of things and I think we are a wee bit away from having that level of detail."
