By Nick Assinder
Political Correspondent, BBC News website
If there is one thing that unites Labour and the Tories above all others it is their determination to do in the Liberal Democrats.
Oaten has quit leadership race
It appears they need not bother too much - the third party is perfectly up to the job of doing it themselves.
At an absolutely crucial point in the party's history, when its optimists believe it is on the verge of a genuine breakthrough, it has stumbled - and is now in danger of falling flat on its face.
First there was Charles Kennedy's revelation, after months of robust denials, that he had a drink problem.
That was enough for some to lose confidence that the party was the most honest of the three.
Then there was the way Mr Kennedy's colleagues disposed of him, which saw the party's, often undeserved "nice" image finished off.
Now there is Mark Oaten's extraordinary, inexplicable belief that he could carry on with a rent boy and not only hold down a high-profile frontbench job, but run for the party leadership, and not get found out.
Kennedy quit over drink problem
It will, therefore, have come as no surprise that the party is facing headlines claiming it is facing its worst crisis for a generation and is collapsing.
And that must indeed be the party bosses' greatest fear.
The Cameron-led Tories were already marching all over their territory - a move largely responsible for the panic which led to the removal of Charles Kennedy (although that was probably bound to come sooner or later in any case).
The leadership election was supposed to draw a line under the Kennedy affair and offer a positive, forward-looking image for the party - much as the Tories' leadership campaign managed for them.
Instead it has turned into a bit of a nightmare leaving interim leader Sir Menzies Campbell attempting to put things back on track.
Thorpe allegations hit Liberal party
The party's leader in the House of Lords, Lord McNally, has also insisted the party has always bounced back from previous setbacks.
That may well have been true in the case of former leader Paddy Ashdown when he confessed to an affair with his secretary in 1992. His poll standing actually increased.
But probably the party's greatest crisis came in the late 1970s when former leader Jeremy Thorpe was at the centre of a sensational court case before being cleared, in 1979, of hiring a hitman to kill a male model to cover up a gay affair.
In those days, the party was gradually advancing in general elections, winning 13 or 14 Commons seats. That dropped back to 11 in the 1979 general election before the Alliance with the SDP gave them a new lease of life in 1983, with 23 seats.
So it is almost certainly the case that, in the long term, the party will survive the latest turmoil.
The job of the remaining leadership contenders is to ensure they put the latest setbacks behind them and re-focus attention on the policy debate raging at the centre of the party - and the vital local elections in May.
They must also be desperately hoping there are no other skeletons rattling in any cupboards...