"EVERYONE knows that politics is a robust trade, especially in an election campaign.

No-one would expect candidates to spend their time highlighting their opponents' virtues but to suggest any smear is justifiable must be wrong."

Fine sentiments - and rather surprising given the author: one Alistair Carmichael.

Writing a Westminster despatch for the Shetland Times in November 2010, the LibDem MP for the Northern Isles was a model of moral authority.

Then the Coalition's deputy chief whip, he was no shrinking violet, for every whips' office is synonymous with intrigue and arm-twisting, favours and threats.

But that only gave his comments more weight: even whips know there is a line not to cross, was the implication, and smearing opponents is beyond the pale.

After his belated confession to leaking a memo to falsely smear the First Minister, Carmichael emerges in a rather different light, as a low-down, conniving sneak.

It is not a good look for the former Scottish Secretary, and not a good look for his party.

Voters do not expect or even want perfection from politicians.

They look for people who understand their lives and can meet their hopes and needs.

But they do expect - and are entitled to - a basic level of integrity.

By engaging in dirty tricks and phoney smears to damage a rival and shore up votes, and then publicly denying all knowledge of it, Carmichael has fallen below that level.

He is a hypocrite caught in a lie and ought to do his electors the courtesy of resigning.

But, as he noted, politics is a robust trade and morality is often second to expediency.

So rather than prompt a by-election in Orkney & Shetland, Carmichael is toughing it out.

His party is behind him. As their last MP in Scotland and one of only eight in the UK, Carmichael is a scalp the LibDems cannot afford to lose.

His majority of 817 would be nigh impossible to defend after a scandal as bad as so-called 'memogate'.

But the LibDems seem to have forgotten next year's Scottish election.

In 2011, the party lost 11 of its 16 MSPs because of cross-contamination as the tuition fees u-turn at Westminster made the LibDems toxic at Holyrood too.

Carmichael's constituency covers two Holyrood seats held by LibDem MSPs.

Tavish Scott in Shetland and Liam McArthur in Orkney proposed and seconded Carmichael as the candidate and signed his nomination papers.

They are already tainted by association.

If Carmichael stays, a local backlash could finish them.

Most people in Shetland voted SNP on May 7, and Orkney was close behind. Both Holyrood seats are in the balance.

Unless Carmichael goes, his colleagues may go instead.

Is one MP worth two MSPs? It is time for a robust choice.