* Twitter, 24-hour media fuel bitter campaign barbs
* Differing popularity scores accentuate rivalry
* One liners overshadow policy debate, rile voters
By Nicholas Vinocur
PARIS, March 6 (Reuters) - From snide one-liners on Twitter to eggs hurled at a cafe sheltering the president, the French election campaign has taken a nasty turn which has left many voters yearning for quieter days - and some decrying a lack of substance in debates.
Hostilities started in earnest when President Nicolas Sarkozy launched his campaign on Feb. 16, drawing gasps with a stump speech accusing Socialist frontrunner Francois Hollande of "lying from morning to night".
The tone has grown sharper as a motley crew of fringe candidates, struggling to make themselves heard above the frontrunners, compete for attention on online news outlets, three 24-hour news channels and in a torrent of Twitter posts.
While Sarkozy has accused Hollande of trying to sound like "Thatcher internationally and Mitterrand in France", referring to the former British and French leaders, a Hollande aide has likened Sarkozy to "a cross between Silvio Berlusconi and Vladimir Putin".
Critics say the constant sniping has pushed aside any real policy debate between the candidates, who have both made fixing the economy their main priority.
"The problem for me is not so much the violence of what is being said as the fact that it masks the absence of a real debate," said Dominique Wolton, a political language specialist at the CNRS research institute.
"The candidates are too close in their positions on many key areas, so they are beating up on each other."
While the tone may not seem shocking from abroad, for many French people it marks an unsettling change from the days when presidential candidates debated politely on state-run radio and television stations, the first of which became private in 1986.
Polls show some voters are tuning out.
An IFOP survey published on Sunday by the weekly newspaper JDD showed that 70 percent found the campaign disappointing, a feeling held by right- and left-wing voters alike.
FIRST BLOOD
At the root of the personal jibes may be the fact that two in three people tell pollsters they disapprove of Sarkozy, whereas Hollande enjoys popularity ratings above 50 percent.
"Hollande is playing almost exclusively on rejection of Sarkozy, which is largely a personal phenomenon," Wolton said.
Sarkozy, seeking to recover from the worst poll scores of any modern-day French President seeking re-election, set the tone from day one by saying his rival was not up to the job.
"Can you think of a single thing that Francois Hollande has achieved in 30 years in politics," he said, recycling a quote that Segolene Royal, Hollande's former partner and the defeated Socialist candidate in France's 2007 election, said during the Socialist Party primary last year.
At first Hollande sought higher ground, invoking the need for "elegance" in the campaign. But, under pressure to show some steel, he fought back accusing Sarkozy of being a "president of the rich" with an "awful legacy".
Hollande, who caused a furore by calling Sarkozy a nasty piece of work during a lunch with journalists, makes a point of rarely mentioning his rival by name, instead referring to him as "the outgoing president".
As the campaign wears on, tempers are flaring.
Sarkozy's entourage was pummeled with eggs and scrunched up political tracts last week on a campaign stop in the southern town of Bayonne, prompting aides to accuse the Socialist Party of having organised a guerilla-style attack on their candidate.
Last week presidential advisor Henri Guaino lost his cool live on television, thumping the table and asking a Socialist guest: "What if I called you a dirty bastard, would you like that?"
With Hollande and Sarkozy dominating the field, other candidates in an April 22 first round have drawn their knives.
Jean-Luc Melenchon, leader of a far-left grouping of parties, clashed with the anti-immigrant Marine Le Pen in a televised encounter last week. After Le Pen said she refused to debate with a man who accused her of being a semi-lunatic, Melenchon shot back: "That leaves you with one good half."
Melenchon previously called Le Pen a "bat", a "pickled reactionary" and an "odious presence", prompting Jean-Marie Le Pen, Marine's father, to challenge Melenchon to a debate in which he would "remove (Melenchon's) underpants".
ANIMAL FARM
Former Prime Minister Dominique de Villepin, who commands around 1 percent support, has compared Sarkozy to a "chocolate rabbit" to be "gobbled up" for Easter, which falls just before the vote.
Green candidate Eva Joly has been hit by a volley of personal attacks via Twitter as opponents mocked her Norwegian accent and quirky appearance, prompting her to try a new style.
No matter how bitter the exchanges, historians note that they pale in comparison to the no-holds-barred attacks of the late 19th century and inter-war period in the 20th century.
"If you take the long view, this campaign is pretty moderate," said Jean-Noel Jeanneney, historian and author of "l'Etat Blesse" ("The wounded state"), a book critical of Sarkozy's presidential style.
"In the Revolution there was a real bestiary of insults: jackal, ray-face, limp boar, old crab, invertebrate, so forth."
"Politics has always required thick skin," he said. "As always, it is those who cause offense who shame themselves." (Editing by Robin Pomeroy)
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