Lord Ashdown said the Deputy Prime Minister had had "17 buckets of s**t" dumped over him by papers like The Sun and the Daily Mail.
Speaking to LBC radio's Iain Dale, Lord Ashdown insisted the party's dismal poll ratings would recover as the "true Nick Clegg" was revealed to voters.
"The right-wing press in this country detest the coalition - detest it," he said.
"If they want to destroy the coalition, what they do is they attack what they consider to be the weakest link and the weakest link is Nick.
"He has had 17 buckets of s**t dumped over his head by these people year in, year out, month in, month out. Of course, that's going to have an effect.
"But I don't think this course is lost and I think that we can reveal the true Nick Clegg before the election and the more we do, the easier the job will be."
A month ago, Lord Ashdown rode to the defence of Mr Clegg after an alleged plot to oust him.
Lord Oakshott, who later quit the party, had carried out private polling on the LibDems' chances with alternative leaders in a bid to undermine Nick Clegg.
Lord Ashdown had described it as a "plot of deep malice" to ditch the Deputy Prime Minister. Mr Clegg has also suffered from poor poll ratings generally.