By Ingrid Melander and Michel Rose
PARIS (Reuters) - All France's presidential candidates go head to head for the first time on Tuesday in a televised debate that will pit favorites Emmanuel Macron and Marine Le Pen against rivals, some of whom draw one percent or less of support in polls.
The marathon three-hour exercise, involving all 11 candidates, will give each candidate only about 17 minutes of speaking time and will be a first for a French presidential election campaign.
With only 19 days to go before the first round of the election, the debate will give challengers like conservative Francois Fillon an opportunity to close the gap on centrist Macron and far-right leader Le Pen.
It will also be, for outsiders like right-winger Nicolas Dupont-Aignan, who has around 4-5 percentage points in opinion polls, and for five candidates who poll between 0 and 1 percent, a rare chance to step into the spotlight.
Debate, which will range over the key issues of unemployment and the economy, and immigration and security, could be heated, French media have suggested.
"We don't want this to turn into a dogfight," said Alain Weil, the director general of SFR media, which owns the BFM TV channel organizing the debate together with CNews television.
Macron and Le Pen are tied on 25 percent in the April 23 first round of the election, although Macron would go on to beat Le Pen in the second round, a Le Monde/Cevipof opinion poll and a separate Ifop poll showed on Tuesday ahead of the debate.
The Cevipof poll, which surveyed 14,300 people between March 31 and April 2, said Macron would beat Le Pen in the May 7 runoff by 61 percent to 39 percent.
The race for the Elysee has been marked by major twists and turns that have seen the eclipse of some big names and the emergence of scandals that have troubled the campaigns of some of the main players.
Fillon, a 63-year-old conservative prime minister, was the frontrunner in the campaign until he was hit by allegations that he paid his wife, a son and daughter hundreds of thousands of euros of public money for minimal work.
He now trails third in the first round, according to polls, a position which would eliminate him from the race.
The Cevipof poll foresaw Fillon getting 17.5 percent of first round votes, unchanged from the last poll in mid-March, while far left candidate Jean-Luc Melenchon was seen getting 15 percent, up 3.5 points and ahead of Socialist candidate Benoit Hamon on 10 percent. (Election graphic - http://tmsnrt.rs/2lPduBG)
Macron, who seeks to transcend the classic left-right divide in French politics, was voted the most convincing performer in a snap poll following a March 20 televised debate involving only five candidates.
Voter certainty has risen sharply in France, with 64 percent of those surveyed now sure of their decision - up 5 points on previous surveys.
The voter base of Le Pen, head of the anti-immigrant and anti-European Union National Front, was the most certain, with 82 percent of her voters sure of their choice, up 4 percentage points.
French judicial police in February questioned Le Pen's bodyguard and chief of staff in relation to a probe into alleged misuse of EU funds to pay parliamentary assistants.
Le Pen denies wrongdoing. She might face questions on Tuesday though on an investigation by a French prosecutor into the activities of her party in a regional council in northern France, news of which broke just hours before the debate.
A judicial source said the probe had been opened after a newspaper report that one of her top party aides was suspected of being paid for fake work.
Fillon's certainty score was up 7 points at 75 percent, Macron's up 9 points to 61 percent, Melenchon's unchanged at 60 percent, and Hamon's up 5 points at 52 percent.
(Reporting by Sudip Kar-Gupta and Andrew Callus; Writing by Ingrid Melander; Editing by Richard Balmforth)