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By Marc Leras and Simon Carraud
MARSEILLE/BIGUGLIA, France, April 1 (Reuters) - France's presidential election race is looking tighter than it was seven days ago, an opinion poll showed on Saturday as the main candidates took their campaigns to the south of the country.
Voting intentions in the April 23 first round for the frontrunners, centrist Emmanuel Macron and far-right leader Marine Le Pen, showed both slipping one percentage point to 25 and 24 percent respectively.
Third-placed conservative Francois Fillon gained two points to 19 percent, and the far left's Jean-Luc Melenchon one point to 15 percent, the BVA poll said.
Complicating predictions, 38 percent of people either could not say how they would vote, or may yet change their minds. That was down two percentage points from a week earlier, but showed that the race remains wide open.
The poll showed independent Macron had solidified his voter base, with 63 percent of those opting for him sure of their decision, up 8 points from a week ago and his highest certainty score since campaigning began in earnest in February.
However, Le Pen still had by far the most solid voter base, with an unchanged 81 percent of her voters certain to pick her.
Shock election outcomes abroad including the U.S. presidential victory of Donald Trump and Britain's Brexit referendum vote have fed expectations that Le Pen's anti-euro, anti-immigration platform could sweep her to power in France.
The poll though, like others this year, showed Macron beating her with 60 percent of votes in the May 7 second round.
Fillon's recovery from the lows that followed a fake work scandal surrounding his wife puts him within 5 points of Le Pen and 6 points of Macron, with some voters previously tempted to abstain deciding to go for him after all, BVA's commentary said.
BVA put Melenchon's climb since a strong performance in the first TV debate on March 20 partly down to more of his natural sympathisers deciding to vote.
It said official Socialist candidate Benoit Hamon, who is in fifth place on 11.5 percent and also has hard left policies, could be vulnerable.
Hamon's base of sure voters is just 45 percent, it noted, and many of them could end up being split - about equally - between Melenchon and Macron.
An Odoxa survey on Friday showed Melenchon just one percentage point behind Fillon on 16 percent, but 8 points ahead of Hamon.
FILLON TURNS BACK THE CLOCK
Le Pen was due to hold a meeting in Bordeaux on Sunday, but it was her two main rivals who were making headlines on Saturday.
Macron met with conservative and security hardliner Christian Estrosi in Marseille, part of his strategy of showing he wants to transcend the right-left divide of French politics.
Estrosi is a key ally of conservative former president Nicolas Sarkozy. He stands a long way to the right of the Socialist government in which Macron was economy minister until last year, but was among those who tried and failed to oust scandal-hit Fillon as the candidate of The Republicans.
Fillon sought to get his campaign back on track by turning back the clock with a warning about France's heavy debts.
France faces the same fate as debt-ridden Greece, he said during a visit to Corsica, reviving the "failing state" controversy he stoked on the Mediterranean island in 2007.
Fillon has based his campaign on the need to rein in spending and cut France's deficit, pledging 100 billion euros ($106.5 billion) of spending cuts and a reduction of 500,000 in the public sector workforce, proposals that are tougher than those of any other mainstream candidate.
It was in Corsica in September 2007, as prime minister under the then newly-elected Sarkozy, that he sparked a political storm by saying he was at the head of a failing state.
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(Additional reporting by Dominique Vidalon in Paris, Editing by Andrew Callus and John Stonestreet)