By Brian Love
PARIS (Reuters) - France's ruling Socialists, staring at prospective humiliation in next year's presidential election, are cranking up their election machine in a bid to re-energise voters disenchanted by Francois Hollande's five years in power.
As they marshaled forces for a weekend rally of leftist groups in Paris, leftist politicians piled pressure on the president, who has yet to say whether he intends to run for a second term.
Hollande has until mid-December to decide. But his approval ratings are at an all-time low for a president, at around 4 percent. Many of those who backed him in 2012 feel, at best, short-changed or, at worst, cheated.
After former prime minister Francois Fillon was elected as the candidate for the center-right Les Republicains last Sunday, the Paris rally gives the left a chance to counter-attack.
Opinion polls make Fillon the runaway favorite to win the keys to the Elysee Palace next May -- and do not even see a Socialist candidate making it into a runoff vote against him.
Saturday's gathering is formally described as the first convention of the Belle Alliance Populaire, or Beautiful Popular Alliance.
Socialist Party leader Jean-Christophe Cambadelis wants the Alliance to bring together leftist politicians, strategists and labor unions behind shared campaign objectives, but the battle may be an uphill one.
Three polls within a week have indicated that Hollande or another Socialist would be eliminated in the first round of voting next April, with Fillon taking some 66 percent of votes in the runoff to crush National Front leader Marine Le Pen.
Arnaud Montebourg, a former minister of Hollande's but now one of his fiercest critics, warned him on Thursday not to try to bypass a Socialist Party primary in January.
"That would be the death of the Socialist Party," he said in a speech in Paris.
Hollande, 62, flies to Abu Dhabi on Friday and is not due back until Saturday, when he could in theory join the left-wing convention and use it to declare his intention to run.
Hollande was elected in 2012 on pledges to target big business and increase taxes for high earners.
But many on the Left were dismayed when he was perceived as failing to take the lead on tax reform.
Grassroots left-wing voters were further alienated by a switch to a more business-friendly line in 2014, by labor laws that brought thousands onto the streets early this year, and by a flurry of Islamist attacks.
However, an Elabe poll published on Wednesday indicated that Socialist Prime Minister Manuel Valls, who has been pushing for a decision from Hollande and said he is ready to run himself if needed, would fare only marginally better than his boss and would also be knocked out in round one.
(Reporting By Brian Love; Editing by Richard Balmforth and Kevin Liffey)