France's Front National hopes for third MP in litmus test by-election

The second round of a by-election in eastern France could see a third MP from the far-right Front National (FN) in the French parliament, although the latest opinion poll showed the Socialist candidate winning.

Posters supporting Socialist candidate Frédéric Barbier (L) and the Front National's Sophie Montel in the Doubs by-election AFP

In a second round run-off, voters in a constituency in the Doubs district bordering Switzerland will choose between Sophie Montel from the FN and Socialist Frédéric Barbier.

The election is seen as a litmus test of how the two parties are faring one month after the Charlie Hebdo attacks in Paris, which party leader Marine Le Pen has said were evidence of a “war declared by Islamist fundamentalism”.

If Sophie Montel wins the runoff, she will become the third FN lawmaker to sit in the National Assembly.

The head-to-head in Doubs shows how the French political landscape is shifting, with the FN increasingly pitched against the struggling mainstream parties - the ruling Socialists or the mainstream right-wing UMP, now led by former president Nicolas Sarkozy.

Le Pen has strengthened support for her party in France by blaming the mainstream parties and the EU for economic slowdown and rising unemployment.

She often lumps them together, under the nickname UMPS.

The outcome of today's election will depend largely on how UMP supporters vote.

The party has been divided over whether to back the Socialists in the name of a “republican pact” to block the FN or the “neither-nor” option of refusing to call on voters to support either candidate.

The party executive this week voted for the latter choice but influential members have publicly criticised the decision.

Sarkozy, who has faced criticism for making a paid appearance at a conference in Abu Dhabi at the time of the meeting, had called for a block against the FN but added that it was up to the voters to decide for themselves.

Speaking at a UMP meeting on Saturday, Sarkozy defended the party line against criticism by President François Hollande, who accused him of not making a clear call to vote against the FN.