Hazel Blears timed her resignation to have the greatest political impact, 24 hours before elections that may decide the Prime Minister's future.
Will she now try to stand against Gordon Brown? (It's not easy under Labour Party rules to challenge a leader, but she may gather support from those who want the PM out).
Her resignation statement contains not a single word of support for Mr Brown: "Today I have told the Prime Minister that I am resigning from the Government.
"My politics has always been rooted in the belief that ordinary people are
capable of extraordinary things, given the right support and encouragement.
"The role of a progressive Government should be to pass power to the people.
"I've never sought high office for the sake of it, or for what I can gain, but
for what I can achieve for the people I represent and serve.
"In this next phase of my political life I am redoubling my efforts to speak
up for the people of Salford as their Member of Parliament.
"I am returning to the grassroots (where I began), to political activism, to
the cut and thrust of political debate.
"Most of all I want to help the Labour Party to reconnect with the British
people, to remind them that our values are their values, that their hopes and
dreams are ours too.
"I am glad to be going home to the people who matter the most to me: the
people of Salford.
"Finally, there's an important set of elections tomorrow. My message is
simple: get out and vote Labour."