Image caption The coalition partners must continue to work together whatever the result

No one likes being labelled a loser.

Politicians fear it more than most.

Come the referendum result, at least one Westminster party leader will be stuck with the tag.

Lib Dem leader Nick Clegg and Labour leader Ed Miliband back the alternative vote. Conservative leader David Cameron opposes it.

It was Mr Clegg's party that demanded the referendum during the talks with the Conservatives to establish the coalition government.

Should the referendum they wanted reject the voting system they prefer, Lib Dem anger will flare, not least among those who expected the prime minister to maintain a lower profile during the campaign

Some Lib Dems, like Energy Secretary Chris Huhne, have already been attacking leading Tories for the way they have argued for a No vote.

Both the prime minister and his deputy insist the work of government will continue whatever the result.

But a No vote would leave enthusiasm for the coalition among doubters among the Lib Dem rank and file shaken.

Should the Yes campaign confound the opinion polls and triumph, the Lib Dems will have something they have long craved - electoral change.

Unhappy Labour?

Many of them will hope it will be a step towards adopting a very different voting system: Full proportional representation, which would deliver the party many more MPs.

If the Liberal Democrats lose the AV vote there should be no renegotiation of the coalition agreement Mark Pritchard, Conservative MP

There is danger too for Mr Cameron.

A Yes vote would be, in the understated words of one of his MPs, a "big problem", not least because as another Conservative backbencher puts it, some on the Tory side think the PM "came out of traps very reluctantly and very late" for the No campaign.

Having failed to win outright at the general election, failure in another national vote would be damaging.

Those Conservative MPs who believe they would lose their seats under the alternative vote would blame Mr Cameron.

But many Tory MPs are quietly confident of a No vote. That result, coupled with coming changes to Parliamentary boundaries that are expected to favour the Conservatives over Labour, would bolster Mr Cameron's party and his own standing.

The concern of some on the Conservative side is not defeat, but how far Mr Cameron will go in shoring up Mr Clegg in the event of a No vote.

Tory MP Mark Pritchard, secretary of the backbench 1922 Committee, said: "If the Liberal Democrats lose the AV vote there should be no renegotiation of the coalition agreement or any retrospective insertion of new policies that were not agreed at the inception of the coalition government."

Whatever the result, Ed Miliband knows some of his Labour MPs will be unhappy. Many have publicly taken a different view from their leader by backing a No vote.

Letwin's 'chuckle'

He will not want to be associated with a losing campaign, but the main focus for many in his rank and file will not be the referendum, but the party's performance in the English local, Scottish and Welsh elections.

In his memoir of the post general election coalition talks, the Lib Dem negotiator and later cabinet minister David Laws recounts the Lib Dems' demands for a referendum on electoral reform.

He recalls the Conservative MP, and negotiator, Oliver Letwin saying: "We will be absolutely straightforward with you on this. Then we will beat you in the actual referendum!"

Then, according to Mr Laws, "he chuckled away in a very Oliver-ish way".

Should that forecast prove accurate, many Conservatives will struggle to stifle a laugh at Nick Clegg's expense.

But they will know Tories and Lib Dems have to carry on working together in the coalition, and Lib Dem troops will have to be kept relatively content.