With just 10 months to go before five million Londoners vote for Britain's first directly-elected mayor, the two ministers have finally offered Tony Blair a serious alternative to Ken Livingstone.
Within hours of Ms Jackson's declaration, broadcaster Trevor Phillips gave a foretaste of the bitter fight ahead when he attacked her record as Transport minister for London.
Mr Phillips welcomed her candidacy but claimed that both she and her Tory predecessor Steven Norris had to explain why the Tube, buses and rail services were so poor.
A spokesman for Ms Jackson said Mr Phillips was lowering the tone of the debate. "It is a little bit sad that Glenda's candidacy is only hours old and some of her fellow candidates have resorted to attacks upon her," he said.
The double Oscar-winning former actress used her new-found freedom to give a round of media interviews yesterday, as her aides said she would confound those critics who have portrayed her as a dour Millbank clone.
Ms Jackson, MP for Hampstead and Highgate, was widely tipped for the axe in the reshuffle, but her entry into the race has been welcomed by Downing Street as proof that "serious" candidates were chasing the Labour nomination. The Prime Minister will not give official or even unofficial backing to any of the runners, but is understood to be keen that the party has the strongest field possible.
Mr Livingstone's continuing popularity with both Londoners and Labour Party members means a heavyweight politician will be needed to beat him should Millbank allow him to stand for the nomination. The probable entry of Mr Banks, who stood down as Sport minister to head a task-force hoping to bring the 2006 World Cup to Britain, would certainly offer a robust challenge to the former GLC leader.
Mr Banks, MP for Newham North West, is a former chairman of the GLC. He shares Mr Livingstone's gift for wit and publicity, but would be much more acceptable to the Labour leadership.
However, the risk of Mr Livingstone winning a ballot of Labour members remains high and party officials may still attempt to exclude him. "Better five months of trouble from Ken supporters than five years of Ken as Mayor," said one Millbank source yesterday.
The Race for
Odds (William Hill)
Jeffrey Archer 5/2
Tony Banks 7/2
Trevor Phillips 5/1
Ken Livingstone 6/1
Glenda Jackson 6/1
Frank Dobson 10/1
Nick Raynsford 12/1
Steven Norris 14/1Reuse content