French President Francois Hollande's Socialists and their allies look set to emerge with a majority after first round voting in parliamentary elections, final results show.
Left-wing and green parties won more than 46% of the vote compared with 34% for the centre-right UMP party, interior ministry figures showed.
The outcome of the polls is expected to determine the extent and pace of reform under the newly elected French leader.
Run-offs are to be held next week.
The turnout nationwide was a modest 57%.
France's 46 million eligible voters have been picking representatives for 577 seats in the National Assembly.
After the first round, 36 seats out of 577 have been declared, according to figures published by the French interior ministry.
TNS Sofres, Ipsos and OpinonWay pollsters agreed the Socialists and their Green allies might win as few as 283 seats or potentially as many as 347. However, potential allies in the anti-capitalist Left Front would take 13-20 seats and ensure a majority.
The Socialists have concluded electoral pacts with the smaller Europe Ecology, The Greens and the Radical Left Party.
Another potential coalition partner is the more radical Left Front, which brings together the Communist Party and the Left Party, and has fielded candidates in nearly all constituencies.
The Left Front, led by Jean-Luc Melenchon, won 6.9% of the vote.
Correspondents say the parties hope left-wing voters will unite around a single local candidate; and that afterwards the parties will be able to combine to form a majority in parliament.
On the right, the UMP - the party of former President Nicolas Sarkozy - has concluded an electoral agreement with its centrist Radical Party and New Centre allies.
But the far-right National Front has ruled out any pact with the UMP.
The election saw a surge in support for Marine Le Pen's National Front, which won almost 14% of votes - way beyond the 4% it achieved in the last parliamentary election of 2007.
However, under France's first-past-the-post system, that would give the party only three parliamentary seats at best and possibly none at all.
The BBC's Christian Fraser, in Paris, says it is hard to predict accurately what the final tallies will be before next week's decisive round of voting. In many constituencies, there will be a three way run-off.
But with the Senate already under the control of the Socialists, it appears that Mr Hollande will also have a majority in the lower house - even if only with the support of allies - which would give him unprecedented power to force through his reform programme.
Mr Hollande's government is due to present a revised budget plan to parliament next month.
The result of the parliamentary election will determine the pace of reform and how radical it becomes, our correspondent says.
"It's a good result tonight... but we have to remain mobilised for the second round," Foreign Minister Laurent Fabius, an influential Socialist, was quoted by news agency AP as saying.
It was a big night for Ms Le Pen on a personal level, our correspondent says.
The firebrand leader of the hard left Mr Melenchon had challenged Ms Le Pen for the seat in the northern town of Henin Beaumont. In the end, he finished third and last night withdrew from the second round race.
"It is normal to be disappointed but we must not be defeated," Mr Melenchon said as he bowed out.
The far right has not held any seats in parliament since the 1980s. The electoral system may yet deny them a seat - but, adds our correspondent, the National Front is now by some margin the third biggest party in French politics.
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