French President Emmanuel Macron is the favourite to win re-election in a two-round ballot on April 10 and 24.

But after a first term mired in social unrest - during which he took steps to liberalise France's labour laws, cut taxes on the wealthy and businesses and tried to reconfigure trans-Atlantic relations - the margins are much tighter than the drubbing he delivered to the far right's Marine Le Pen in 2017.

Here's a look at the leading scenarios for the decisive second round of the election:

 

MOST LIKELY: MACRON - LE PEN

Le Pen is the most likely candidate to face Macron in a second-round runoff. She has surged in polls as she rows back on her more pugnacious rhetoric and delivers voters a simple message: I'll put money back in your pockets.

Le Pen's ratings suggest she has been successful in de-demonising the image of her far-right party, without actually changing its core, anti-immigration platform.

Surveys show her winning up to 23% of first-round voting intentions.

In a runoff against Macron, polls project she could secure as much as 47%-48.5%, putting victory within the statistical margin of error. Abstentions and undecided voters could spring a surprise.

 

SURPRISE SCENARIO? MACRON - MELENCHON

The hard-left's Jean-Luc Melenchon is polling third and edging higher. His supporters are hoping for an upset.

With the traditional centre-left Socialist Party verging on irrelevance and the Greens struggling to galvanise a wide support base, Melenchon has appealed to left-wing voters to rally behind him.

He is now polling at 14%-17% in voter support surveys compared with 9%-10% in January for the first round. Polls see Macron easily beating him if he makes it to the second round.

 

UNLIKELY: MACRON - ZEMMOUR

The rise last year of Eric Zemmour, a talkshow star who channels ex-U.S. President Donald Trump's anti-establishment style as he paints himself as the would-be saviour of a nation under a perceived threat from Islam, upended the early campaign race.

Last year, some surveys showed Zemmour reaching the second round, but his support has fallen back as he struggles to formulate ideas beyond immigration and security and has been hurt by his comments on Russia.

But opinion polls now show him winning 9%-11% of votes in the first round, far behind Le Pen and Melenchon.

Macron would comfortably defeat Zemmour in a second round, polls have shown.

 

UNLIKELY: MACRON - PECRESSE

The head of the greater Paris region, Valerie Pecresse, who describes herself as part Margaret Thatcher, part Angela Merkel, won the conservative Les Republicains' ticket in December, which gave her a boost in opinion polls.

However, she has seen her campaign falter as she struggles to set herself apart from Macron while countering the nationalist programmes offered by her far-right rivals.

Recent opinion polls show her winning only 8%-10% of votes in the first round.

 

HIGHLY UNLIKELY: MACRON OUT OF THE RACE

No opinion poll sees Macron failing to qualify for the April 24 runoff.

(Reporting by Richard Lough and Ingrid Melander, Editing by Peter Graff, Timothy Heritage, William Maclean and Nick Macfie)