Gordon Brown is not now likely to face a heavyweight challenge for the Labour leadership when Tony Blair stands down this week.
Gordon Brown is unlikely to face a Cabinet-level challenge
Mr Brown could still face a challenge from one of two left-wing backbenchers.
But Home Secretary John Reid's surprise announcement that he will be voting for Mr Brown effectively ends the prospect of a Cabinet-level contest.
Mr Reid has said he will quit frontline politics at the end of June "when Mr Blair goes".
Mr Blair is expected to announce a timetable for his departure on Thursday - but will continue to serve as prime minister during a seven week Labour leadership and deputy leadership contest.
He has already said he expects Mr Brown to take over as prime minister "within weeks" and has repeatedly praised the chancellor's stewardship of the economy.
But in an article for the News of the World, he appeared to go further by suggesting Mr Brown could lead the party to a fourth consecutive election victory.
Mr Blair argued acknowledged Labour had a fight on its hands to win a fourth term but he insisted it could bounce back from Thursday's setbacks at the polls in Scotland, England and Wales.
But he said the Tories' policies were a "mess" and were not "not thought through".
He went on: "Gordon Brown by contrast is completely thought through.
"He has steered our economy from one of boom and bust to one of the best in the world.
"He didn't do it by choosing the easy way. He did it by sound judgment, holding his nerve and putting the long-term interests of Britain first.
"At general election time, that is still the route to victory."
The Lord Chancellor, Lord Falconer, also predicted that Mr Brown would become prime minister.
He told Sky News: "That would be my judgment, that Gordon Brown will be the next leader of the Labour Party."
He added: "Gordon Brown is a towering figure in the Labour Party.
"I don't think it's right to have a contest when there is no appetite for one.
Asked whether Mr Brown could lead Labour to general election success, he said: "Without doubt."
Work and pensions secretary John Hutton - another key Blair ally tipped at one time as a possible leadership challenger - also threw his weight behind Mr Brown, telling GMTV he would "do everything I can" to help the chancellor.
On Friday, former Home Secretary Charles Clarke - long tipped as a possible Blairite challenger - said he would not be standing against Mr Brown.
Education Secretary Alan Johnson, who is bidding to be Labour's deputy leader, welcomed Mr Clarke's decision not to stand.
"I think Gordon is superior in the sense of his intellect, his experience, his drive his energy, that everyone including me thinks he's the best candidate," he told BBC1's Sunday AM.
Mr Johnson added that Labour would enjoy a "bounce" if Mr Brown took over from Mr Blair.
But former environment minister, and leadership hopeful, Michael Meacher said he doubted Mr Brown's ability to turn the party around, arguing New Labour had "run its course".
"Whoever is the new leader, it's not just a question of changing the face, it's a question of reinvigorating, exciting the enthusiasm and imagination of our supporters. We clearly lost it," he told BBC1's Sunday AM.
Mr Meacher said he and fellow left-wing challenger John McDonnell had made a deal that they would not stand against each other for the party leadership.
The pair will decide in the middle of this week which of them has the most support and throw their weight behind that person.
Mr Meacher said it was "very likely" one of the two would achieve the support of the 44 MPs needed to enter a leadership contest against Mr Brown.