The scale of Labour’s defeat in Crewe and Nantwich — and the 17.6 percent swing to the Conservatives — completes a month of misery for the party at the polls. David Cameron’s success in decontaminating the Tory brand meant disillusioned Labour voters saw his party as an acceptable vehicle by which to deliver a bloody nose to Gordon Brown’s government.

The Conservatives are electable. They are favorites to win the next general election, too. But it is not a foregone conclusion that they will win it. Instead, this month has marked the end of a decade and a half in which the normal laws of political gravity were suspended. There was only one electable party in British politics between the ERM crisis of autumn 1992 until David Cameron’s election as opposition leader at the end of 2005. That period is over. Labour has not yet understood or adapted to this change, relying too heavily on an outdated 1990s campaign textbook and script that will no longer work.

Crewe and Nantwich counts as a famous victory for the Conservatives in part because of the scale of their victory, but also because of the unparalleled historic failure which has preceded it. The “toxic Tories” made no by-election gains during the last 11 years in opposition, though governing parties had lost seats directly to the official opposition in by-elections during every Parliament since 1955 (excepting only the short six-month Parliament in 1974).,Though many political memories at Westminster do not go back before 1997, in fact, the Crewe swing registers only in the middle of the Richter scale of historic by-election earthquakes. Labour is in dangerous territory, but the history suggests that this is not mission impossible yet. Everything depends on whether Labour can use the next two years effectively to offer a real choice at the next election.

First, Labour needs to understand that a strategy built on a “Keep the Tories Out” slogan will not be enough to win. As late as 2005, the argument that “the Tories haven’t changed” was just about enough to see an unpopular government home. Of course, Labour must challenge and scrutinize the Tory claim to be ready to govern, but that won’t succeed without its own positive message, too. That argument wasn’t clear enough in London or in Crewe. And Labour must play the ball, not the man: what their opponents believe, not where they come from.

Second, the Crewe defeat clearly shows that Labour’s heartland support is unhappy, unclear about what Labour stands for, and unsure that the party wants to stand up for them. Every serious contribution to the post-local election inquest has emphasized that a Labour fight back must reunite a broad electoral coalition, addressing northern and southern discomfort, not debating whether it should choose to appeal to heartland or swing voters. This also means that the uber-Blairite critique of Brown is less convincing after Crewe. What, apart from presentational advice, is being offered on substance that would have improved this result, rather than making it worse? The voters of Crewe were not crying out for bolder reforms of the public services. They wanted to give Labour a bloody nose over the 10p tax rate and the closure of post offices.

Brown’s problem is not that he has deviated too far from a winning New Labour formula which could still deliver again. The problem is that, having rightly promised “change”, is that there has been too little clear and visible change. Brown has yet define his agenda convincingly to the public at large.

Third, Labour must now think and fight politically as an opposition party would, while using its power to govern over the next two years to offer concrete challenges to its opponents. The aim must be to restore its own reputation for fairness, and test the opportunistic “magpie” raids which the Conservatives have made.

Cameron says he leads the “progressive” party of the NHS and the low-paid. Labour should be eager to fight over this territory. The party that created the NHS could phase out prescription charges; the party that introduced the minimum wage could end the lower rate for those under 21; the party that believes in progressive taxation should present a package which reduces child poverty and does ask the top 1 percent of earners to contribute more to make this possible.

It is quite possible that the Conservatives would, tactically, decide to support much of this. That would see Brown extend and entrench Labour’s legacy, and begin to make the political weather. If they do not, Labour would develop popular dividing lines between the two parties which could resonate with voters. They are sorely short of these right now.

Gordon Brown has had a difficult year as prime minister. Of course, there have been mistakes and self-inflicted blows. The fallout of the 10p rate has done more damage than last autumn’s election speculation, because it has seemed to undermine Brown’s core mission in politics. The answer must be to reassert that vision, placing the war on child poverty at the centre of his agenda.

But to see Labour’s problem as simply as issue of Gordon Brown’s leadership is far too shallow. Nothing in the challenge of message, strategy and policy — how to define the choice at the next election which could see off the call of “time for a change” — would be solved by having a different personality in charge.

Brown will never win back the favor of the media — which exaggerated his bounce last summer, while writing off Cameron, and now does the opposite — unless he restores his own political fortunes first. So Brown should ignore the media, embrace the status of the underdog and launch a Harry Truman-style fight-back campaign, by picking the political fights with his opponents that can upset the odds.

A bolder Brown remains the Labour figure best placed to reassert his party’s claim to be the party of fairness. This is what he came into politics to do. It is also now the agenda on which his and his party’s political future depends.