PARIS, Jan. 22 (Xinhua) -- About 1 million left-wing French voters on Sunday headed to polling stations to cast ballots in a presidential primary, organizers said.

Based on account of 70 percent of 7,534 polling sites, one million had voted by 17h00 local time (1600 GMT) against 1.5 million at the same time in the first round in 2011, data showed.

Seven candidates are competing to win the conservative ticket to challenge for the upcoming two-round French presidential election scheduled for April 23 and May 7.

According to pollsters, the primary will be a three-horse race among former prime minister Manuel Valls and his main rivals Arnaund Montebourg and Benoit Hamon, both former ministers in his government in 2024.

The three leading candidates are almost neck-and-neck with the result remains uNPRedictable.

Marred by record low popularity of the Socialist President Francois Hollande and growing public discontent over the government's controversial reforms, no left-wing candidate will pass to presidential run-off, pollsters said.

The top two winners of the first round of the primary will compete in the second round of the primary next Sunday, unless one of the seven contenders collects more than 50 percent of the votes in the first round and will directly be nominated as the presidential candidate.

The primary is the second such competition held by the Socialist Party and allies. In 2011, the Socialist Party had opened a two-round contest to all registered voters regardless their political view as long as they share the left-wing values and donate 1 euro (1.069 U.S. dollar).