Which would you prefer as your president, the left-wing newspaper Liberation asked in an editorial on Thursday: a Trotskyite or a dirty dealer?

A frivolous question, perhaps, but one which reflects the growing personalisation of the political battle here.

Because less than a year now ahead of the presidential elections, it is clear that the gloves are off.

Both Prime Minister Lionel Jospin and President Jacques Chirac have ammunition in reserve that they feel can sink the other's campaign. And increasingly, it seems, they are prepared to deploy it.

'Trotskyist mole'

An outburst by the prime minister in the National Assembly on Wednesday was a sign of how sensitive he feels on the issue which risks becoming his Achilles' heel.

He thought he had answered the allegations about his Trotskyist past when he came clean last week and admitted he had been associated with a revolutionary party in the 1960s.

But it seems there is more.

A respected news magazine reported this week that Mr Jospin stayed in the party - the OCI - when he joined the Socialists in 1971, and as late as 1982, when he was Socialist party secretary, was still having secret meetings with the OCI's leadership.

It was this charge that he was in essence a mole inside the Socialists - a charge he has never answered - that provoked his tetchy response in parliament, and what he did was swivel the spotlight round on his rival, the president.

Twisting the knife

"OK," he said, "I was slow about revealing my Trotskyist past - but that is better than refusing to talk at all to a judicial investigation."

The reference to President Chirac's difficulties was not difficult to decipher.

His weak spot, as everyone knows, is the weight of evidence suggesting he at least knew of the illegal financing of his RPR party when he was mayor of Paris.

His refusal to testify before a judge looking into the scandal - on the grounds that it would sully the dignity of his office - has already been seized on by the left as a sign of his guilt.

Mr Jospin was just twisting the knife.

So the mud-slinging has started. The sad thing is that both issues are important.

If Mr Jospin was indeed a secret agent of the far-left, that is a very grave matter. As are the charges weighing against Mr Chirac.

Each side has a perfectly legitimate right to target the other, but the risk is that in the crossfire every other issue will be blitzed out of existence.