By Richard Balmforth and Dominique Vidalon
PARIS (Reuters) - French voters can expect verbal "hand-to-hand" combat when centrist Emmanuel Macron and the far-right Marine Le Pen hold a televised debate on Wednesday night, their last encounter before Sunday's run-off vote to pick the next president.
Opinion polls show Macron, 39, holding a strong lead of 20 points over the National Front's Le Pen with just four days to go to the final vote, in what is widely seen as France's most important election in decades.
Voters are choosing between Macron, a strongly Europe-minded ex-banker who wants to cut state regulations in the economy while protecting workers, and Le Pen, a euroskeptic who wants to ditch the euro currency and impose sharp curbs on immigration.
Macron finished only three points ahead of Le Pen in the first round on April 23, but he is widely expected now to pick up the bulk of votes from the Socialists and the center-right whose candidates were eliminated.
Though Le Pen has a mountain to climb to catch Macron, the campaign has been packed with surprises, the exchanges between the two have become noticeably sharper and the 48-year-old National Front veteran has shown she is capable of catching him out with clever public relations maneuvering.
Upwards of 20 million viewers are expected to tune in to the debate out of a voter population of close to 47 million.
Macron warned he would not pull his punches against a rival whose policies - primarily the anti-euro strategy and a nativist anti-immigrant policy on jobs and welfare - he says are dangerous for France.
"I am not going to employ invective. I am not going to use clichés or insults. I'll use hand-to-hand fighting to demonstrate that her ideas represent false solutions," he told BFM TV.
Le Pen, who portrays Macron as a candidate of high finance masquerading as a liberal, told Reuters: "His program seems to be very vague, but in reality it is a simple continuation of (Socialist President) Francois Hollande's government."
ABSTAINERS TARGETED
In that interview she reaffirmed she wanted to take France out of the euro and get a national currency back into French pockets within two years.
A Cevipof poll published on the website of Le Monde on Wednesday - one of the last big polls before the Sunday vote - saw Macron getting 59 percent of the votes versus 41 percent for Le Pen, similar to other pollsters in the last few days.
The poll said 85 percent were now sure which way they would vote, leaving at least 15 percent of voters who could be swayed by what they see and hear in the TV showdown.
Commentators said Wednesday's debate could still have an influence, particularly on potential abstainers, many of whom voted for the candidate of the hard left who came fourth in the April 23 first round.
"What he (Macron) has to do is to convince the people who didn't vote for him (in the first round) and who do not agree with his program that they will be respected," one outgoing government minister said.
Macron, a one-time economy minister in a Hollande Socialist government, heads only a fledgling movement called En Marche! (Onwards!) which has no representation in parliament.
Assuming he wins, one of his immediate challenges will be to build a parliamentary majority in follow-up elections in June to push through his program and avoid being hamstrung by a National Assembly where opponents hold sway.
If Le Pen wins on Sunday but fails to secure a parliamentary majority, she would dissolve the National Assembly and call a fresh parliamentary ballot under new proportional representation rules - assuming that new voting system was endorsed in a referendum.
The center-right Republicans, still a major force even after their presidential candidate Francois Fillon crashed out in the first round, hope the parliamentary elections will give them enough power to force Macron into a power-sharing arrangement.
Francois Baroin, a leading light of The Republicans who sees himself as a prime minister if Macron accepted such a deal, told RTL radio: "Macron is a man of the left and he'll swing to the left. I'll be voting Macron on Sunday, but France will not get any reform with him."