French left-wing voters are casting ballots in a nationwide presidential primary aimed at producing a candidate strong enough to confront formidable conservative and nationalist rivals in the April-May general election.
Seven candidates from the Socialist Party and its allies are running in Sunday's first round of voting. The top two advance to a run-off next Sunday.
Centre-leaning former prime minister Manuel Valls is a leading contender but faces formidable challenges from Arnaud Montebourg and Benoit Hamon, both former government ministers.
The primary's winner will have tough competition from candidates on the far left, centre, right and far right in a campaign marked by anti-immigrant populism and economic stagnation.
President Francois Hollande declined to seek re-election, fearing his record-low popularity would hurt the Socialists' chances of keeping the presidency.
