French President Francois Hollande's Socialists and allies were headed for an absolute majority to push through tax-and-spend reforms after a first round of parliamentary elections Sunday, exit polls said.
The election also saw a surge in support for Marine Le Pen's far-right National Front, which wants to ditch the euro and battles against what she calls the "Islamisation" of France.
Estimates released by pollster CSA after voting ended put the Socialists and their Green allies at around 40%, well ahead of the 35% score of ex-president Nicolas Sarkozy's right-wing UMP party.
Hollande, who defeated Sarkozy in presidential election, wants voters to give him a strong mandate to enact reforms as France struggles with Europe's debt crisis.
If results are mirrored in next week's second round, that will boost Hollande's status in Europe as champion of the movement away from the German-led fixation on austerity.
The CSA poll put the National Front, whose leader got 18% of the votes in the first round of the presidential election, at more than 13%, far above the 4.0% it got in the last parliamentary election in 2007.