TIED into a union of which both parties are weary, Britain’s Conservatives and Liberal Democrats are increasingly leading separate lives. Although relations between senior politicians remain strong and the coalition seems likely to last until the 2015 general election, Tory and Lib Dem MPs have come to openly loathe their supposed allies—and often hold their leaders in contempt for compromising with the other side (see article). Some departments now feature open rows between ministers. Both David Cameron, the Conservative prime minister, and Nick Clegg, his Lib Dem deputy, feel a growing partisan tug from their angry backbenchers.

The parties are already moving to stake out territory on which to fight the election, differentiating themselves from each other and lobbing the odd grenade. A leaked memo from Mr Clegg to his party urges sustained attacks on the Conservative Party as a heartless rich man’s club. The Conservatives are preparing to campaign as the only party capable of taking tough decisions on welfare and the public finances.

Until death do them part

All this is understandable. Both parties have slipped in the polls. Their leaders are under pressure from MPs and activists to assert themselves. But it is bad for the country and self-defeating for the two parties. Come the next election, voters will judge the coalition partners on three things: the economy, their leaders and the government’s overall competence. The economy is (broadly) on a set course. The Tories, at least, will stick with their leader. Hence the importance of competence—and the smaller the gap between the parties, the greater the chance of the government looking effective in 2015.

Amid the boos and backbiting it is easy to forget that this government started in a notably effective way. It speedily began a bold programme of deficit-reduction, from which it has deviated only in mostly sensible ways as the global economy has struggled. By comparison, much of continental Europe has been tardy. The coalition followed that up with bold reforms to almost every public service. Schools, hospitals, local government, police, the armed forces—none has been spared.

Some of these reforms are progressing quickly (especially the freeing of schools to manage their own affairs). Others have stalled. An attempt to transform the National Health Service was poorly launched and is still bogged down. Police reform is dangerously in the balance: elected police commissioners, who can hire and fire chief constables, are moving into their new offices. But few people voted for them last November, and nobody knows how they will work out. The welfare system awaits a brutal test this year: the folding of numerous benefits into a single “universal credit”. If this goes wrong—and big government IT projects often do—the country’s neediest people will suffer badly.

The coalition could, and should, embark on new reforms, chipping away at the green belts that constrain development around big cities, for example. But its main task is to see through the revolution that it started in 2010. The programme is hugely ambitious, especially given the lack of money available. It is also broadly right—and some reforms that are not right, such as the elected police commissioners, cannot now be reversed. Even health reform can be rescued (see article). Finishing the job would be good for Britain.

And good for the coalition parties, too. Voters do not pay much attention to the details of things like welfare reform, but they know whether crime is rising and how long they must wait for a hospital appointment. Harmony does not ensure competence, but tends to encourage it. Unity over deficit-reduction and schools has turned those reforms into juggernauts, capable of riding over bumps. Disunity has crushed health reform, caused business policy to drift and now threatens to knock welfare reform and energy policy off the road.

Differentiation will save neither the Conservatives nor the Liberal Democrats from the devastating perception that they have run the country poorly. They might as well renew those marriage vows: there are still another 28 months to go.