The government had even called back Foreign Secretary Jack Straw from a trip to Moscow and Finance Minister Gordon Brown from the Middle East to make sure they were present to cast their votes.
In the end, however, the proposal was soundly defeated -- with 291 for and 322 against.
A defiant Blair -- in a television interview tonight -- rejected the idea that the rejection represented a vote of no confidence in his government.
"It is sometimes better to lose and be right," Blair said, "than to win and do the wrong thing."
Home Secretary Charles Clarke had earlier tried to convince lawmakers, stressing that it was the police who had requested the 90-day detention period.
"I notice that that is what the overall majority of the British people agree, too," Clarke said. "I regret that some parliamentarians -- the front benches of the other political parties -- are not prepared to listen to the police in this regard, and I think they should."
In the end, though, a bigger threat for the government than the opposition parties was a group of almost 50 rebels from within the Labour party itself who voted against the proposal.
An alternate proposal to extend the detention period from the current 14 days to 28 days did pass, however.
Earlier today, trying to make his case, Blair had told parliament that police had foiled two terrorist plots since the 7 July attacks in London.
"We are not living in a police state, but we are living in a country that faces a real and serious threat of terrorism, terrorism that wants to destroy our way of life, terrorism that wants to inflict casualties on us without limit," Blair said.
Many civil rights organizations supported the stance of the opposition Liberal Democrats -- that is, that the 14-day provision for detention of terrorism suspects is sufficient.
"We're very concerned at this particular proposal," said Doug Jewell is a spokesman for the National Council for Civil Liberties. "We feel that it is a very broad power, which will lead to miscarriages of justice if it's actually put on the statute book."
Many terrorism experts had their reservations, too.
Paul Wilkinson chairs the Centre for the Study of Terrorism and Political Violence at the University of St. Andrews in Scotland. He said the police have a "very strong case" for arguing that they need more time to question terrorist suspects:
"Some suspects today have very sophisticated computers with a great deal of information that the police would need to take from the hard drive," Wilkinson said. "They may have complex links, including internationally, which would mean there has to be time for investigators to follow up leads abroad."
But Wilkinson felt, too, that the 90-day period could have alienated the Muslim community.
"We also have to remember that the Muslim community would be very alienated if it became assumed that 90 days became the standard time for those suspected," Wilkinson said. "I think we have to take a balanced approach and recognize that many of these investigations could be completed far more rapidly."
The government did compromise, agreeing that any detention would need to be extended every seven days by High Court judges. And it also said the provision would be reviewed after one year.
But it was not enough.
Michael Howard, the leader of the Conservative opposition, said Blair's authority has now been diminished "almost to vanishing point." He said the vote shows Blair is no longer able to carry his own party with him and that he "must now consider his position."
Blair has said he has no intention of resigning.